For federal unsubsidized and grad-plus loans, complete your FAFSA and input all your potential schools when filling it out. Those schools will receive your information and if you are an accepted student, they will give you a financial aid offer (loans will be offered to the full cost of attendance minus scholarships/grants). You need to have your FAFSA completed as soon as possible since grant/scholarship funding is limited. Loans need to be accepted before you pay tuition. For private loans, you simply fill out the company's application; however, this is typically discouraged considering federal loan interest rates are only currently 6.08-7.08% and private loans range much higher, have variable apr's, and require a credit-check. If you have more questions, feel free to ask!
-Daniel (currently taking loans out for the Fall lol)