All you really have to do is submit an application to a lender online, over the phone, or in person. You should include information such as proof of identity, income, and residence. The lender will then review your application and determine your approval amount and interest rate. It really is as simple as that, but you will probably benefit from seeking out a lender that you already have a relationship with. It is also a good idea to shop around to get pre-approved for the best terms before heading to the dealership.