When you have bad credit it's not a very easy task to get a car loan.
You'll need to search around and check out car dealerships that will work with you on getting you into a used car for a certain amount of money down.
There are car dealerships that advertise that they work with you on bad credit and will help you get financed and some car dealerships do have some in house financing where the car dealership will do like a rent to own payment plan on the car loan through them.
You put some amount of money down on the car depending on your credit and the amount of the car loan and then sign some paperwork and you can drive off in it.