How do I buy a used car?

I barely moved here i am a 19 yo who got his SSN for the first time, I just got in the country so I don’t know about the process of buying a car, I thought in buy a dealership car but was too expensive by the interest rate, so I thought on la car lot because it’s cheaper and fair I think, so I got the option of buy a used one in marketplace assuming all the riks that may have, what is the best way to buy a car w $3000? And after that what’s is the title an insurance process? I’m new with formalities too