Hey there, Zack here from Online DMV, here's what you need to do to register your car...
For a used car, the first thing you need to make sure is that you get the title signed over to you. You then need to ensure that you have a bill of sale for that car, proof of insurance for the car, and a valid ID.
I'm not sure which state you're trying to register the car in, but you might also need to get a smog check or go through a vehicle inspection. In some states (again, please make sure you check your state's laws), you can normally drive a car temporarily with just a bill of sale and a transit permit, but only if you qualify.
I hope this helps
