Your loan servicer will provide information about repayment and will notify you of the date your loan repayment begins. It is very important that you make your full loan payment on time either monthly (which is usually when you'll pay) or according to your repayment schedule.
If you don't, you could end up in default, which has serious consequences (see What is Loan Default?). Student loans are real loans - just as real as car loans or mortgages. You have to pay back your student loans. In fact, student loans are one of the few debts that cannot be erased by bankruptcy.
Can you repay your loans while in school? Yes! Contact your loan servicer through www.nslds.ed.gov.