This is part of the process to create your first Personal Vehicle, which will remain your only ' property' until level 5. When you create a new character in GTA Online, as part of the creation process Simeon will phone you to offer you some free customisation. Drive to the nearest Los Santo Customs and purchase a tracker and insurance for the car and its yours, with the free bulletproof tires upgrade.
When the mission is over you will spawn back into the game you will still have possesion of the Dominator.
Let the other person go there alone while you remain seated in the Dominator. During this mission you will receive a Vapid Dominator equipped with bulletproof tires, Complete the objectives until you have to drive to Lester's compound to end the mission.
For this glitch you wil need at least 2 people and 1 one of them must be able to get the mission from Lester called (Cops capacity).