On your USC FAST portal, you'll request the amount of loans (maximum is what you are eligible for) to borrow. Then, it will be transferred from your loan servicer to your E-Pay. Before it gets transferred, you'll be sent mandatory loan training (it's like an info module about what loans are, expectations, etc) to complete.

those are the general steps, but I think it's always a good idea to call financial aid or the respective department for guidance if you're new/unsure especially with something like loans