Just go to your local insurance agency. They will register the car for you and fill out all the paperwork and give you a license plate all at once. I think they charged around 20 bucks or so in addition to the insurance that I had to pay. Your insurance could be a little higher but you can always switch after a year once your paperwork is all set.

I did this about 2 years ago, tho we paid (small amount) for the car from our parents.