Getting the loan requires some shopping.
A good rule of thumb is to have your financing in order before you even set foot on a car lot or in a dealer showroom. Used car lot loans are notorious for their loan-shark interest rates. When dealers arrange financing, they do not really have your interest at heart, plus they get a cut, so your loan will end up costing a lot more than if you do it yourself.
Approach a bank or a credit union, hopefully one where you have had an account for some time. Credit unions are especially inclined to help young borrowers, especially those who have already started a good credit history as outlined above. When you walk onto a car lot with your financing already approved, your car deal-making is going to be a lot smoother. Never let the dealer know how much you have to spend.
Online car loan lenders are available as well. You can even find brokers who will take your preliminary information and do a search for lenders who can best meet your desires regarding interest rates and repayment terms. You can pick among those. As with any online transaction, be sure the site is secure. You might want to check the Better Business Bureau for ratings or customer feedback on the lenders you are considering.