This one question in different forms has been asked in general specific to the gaining of Samadhi and there is much research that needs to be done by the individual to be able to first sit in the state of Samadhi in order to understand the answer.
Is going to be a little difficult trying to explain by posting here as the state of Samadhi is gained through experiential knowledge after one has Accomplished the states of Dhaaranaa, the ability to concentrate on an object that leads one to the next natural state of Dhayaana that is the state of Consciousness where the mind is flowing in an unbroken current toward an object more on this later however once the mind is flowing in this unbroken current the state of Samadhi will manifest itself within the aspirant.
What the books don't usually tell a person is that the object mentioned can be a physical object or visualization or a Mantra or series of Mantras.
There are a number of ways to get to state of Samadhi so am suggesting that after I try to explain what I have found then you go to your Guru for more information or go to internet and look up the works of Maharishi Patanjali and his teachings on Patanjalis Sutras. The Chapter on Powers, atha vibhuuti paadah and The Chapter on Kaivalya atha kaivalya paadah.
There are three stages on the way to Sanyama or Oneness with an object or what is described as the perfect regulation of Chitta and Samadhi is only one of the three stages leading up to Sanyama the purpose of going to state of Samadhi is so that you can practice Sanyama and introduce intent and purpose at this level to change your life in the relative work a day life.So I would suggest that your question be changed to how to do Sanyama with Parad Shiva Lingam as this is one state beyond Samadhi and is a state of Ultimate One Ness with the object of intent and purpose.
Can only detail to you from what I was taught and that is a person first goes to Samadhi with Mantra again I have heard also that sometime visualizations are used in some Meditation Techniques. However, a person first needs to know how to meditate and attain Samadhi through the first three stages of meditation.
Your question was how to get into Samadhi with Parad Shiva Lingam however you don't have to stop there if you wish. If you wish you can go one step farther and do Sanyama with the Parad Siva Lingam. one way I can suggest is that if you use the Parad Siva Lingam as the object of concentration in your meditation then you will have to be sitting in Samadhi with eyes open or half closed or totally closed and then with unbroken concentration worship as you need to by deliberately introducing intent and purpose or worshipping with hymns to Lord Siva.
Will go through this again in a little different manner, it is stated in texts that Samadhi is one of three states of Consciousness leading to the aspirant performing Sanyama on an object. Again what is not explained in many texts is that the object can be a physical object or it can be a Mantra or a series of Mantras meant to worship your Ishta Devata or other Deities. All this leading to a positive change in the relative field or everyday world the meditator is living in. However, sitting in state of Samadhi is necessary for all this to Manifest at the will of the Meditator. Samadhi leads to the option for the meditator to simply sit in Samadhi or go to the next level of practicing Sanyama on an object in your case you would be practicing Sanyama on the Parad Siva Lingam if this is what you wished to do.
In this place of consciousness in time and space that is called Samadhi is the Field of All Possibilities and is the culmination of the process of Dhaaranaa and Dhyaana leading to Samadhi. If you know how to get to Samadhi through meditation then the meditator deliberately introduces their intent and purpose to this Field of All Possibilities this is called doing Sanyama on an object with deliberate intent for results and positive change and this is where the 11 Mukhi Lord Hanuman Rudraksha helps the wearer as this Holy Rudraksha destroys the obstacles to Meditation and helps with the yogic practices.
By doing this practice of meditation the meditator initiates Sanyama on the object of choice, this choice can be the Accomplishment of the Siddhis and Riddhis as mentioned in the Holy Books and this is also where the 8 Mukhi Lord Ganesha Rudraksha helps the meditator to move and remove all obstacles on all levels of existence.
This Field of All Possibilities that can be called the Unified Field in Physics is also the state of Consciousness from where the missiles are thrown Missiles that are the Mantras that are the Energy Forms of the Devas as described in the Ramayana Balakanda and Vasisthas Dhanurveda Samhita.
If you wish to read more about the Missiles given to Lord Rama for Protection as mentioned in the Ramayana Balakanda you can read the book Vasisthas Dhanurveda Samhita in chapters named Weapons and Purification of Weapons by Hymns and Paasupataastra. These books will explain the Mantra Science of throwing and warding off missiles for protection and the good of all concerned. To go over this again; Maharishi Patanjali Teaches clearly states that in order to do Samyama there are three stages of consciousness one must first attain. Samadhi is only one part of the three.
First in meditation there is Dhaaranaa or the ability to concentrate on an object and this is where the One Mukhi Rudraksha and the 11 Mukhi Rudraksha and 8 Mukhi Rudraksha helps the wearer to maintain the ability to concentrate on the object selected.
Once the ability to concentrate on an object without interruption is Accomplished this leads naturally to the state of Dhyaana where the mind is locked into flowing toward that object in an unbroken current; an unbroken current that is not interrupted by any other thoughts pairs of the 3 Mukhi Lord Agni Rudraksha and 5 Mukhi Kaalagni Rudraksha help in this process as these two Holy Beads are credited with destroying past and present Karma that would interfere with the unbroken current of thought the 3 Mukhi by burning away the thoughts that might break the concentration and the 5 Mukhi Guru Bead that continually works to calm the fire as the Karma is burned.
Once the process of Dhyaana is accomplished the aspirant will naturally gain a state of Samadhi or One Ness with the object of concentration and again in your case this would be One Ness with the Parad Siva Lingam and all that it represents.
As different people will have different techniques to help you with your wanting to sit in Samadhi with the Parad Siva Lingam, I am hoping this explanation here helps to clarify a part of Mantra Science that combines Meditation with Rudraksha and other Holy Items to Accomplish in an accelerated manner for the good of all concerned.
"Aum Namah Shivaya Shivaya Namah Aum"