You are not required to use student loans to help pay for tuition. However, you are given this option after filling out the FAFSA. If you choose to use student loans for school, you must choose the amount you accept (up to the amount offered), and you are also given the option to cancel the loan in the future.
If you want to use student loans, there will be two additional documents you will need to complete other than the FAFSA: Entrance Loan Counseling and a Master Promissory Note. These documents can be found at www.studentloans.gov and should be signed with the FSA-ID created when completing the FAFSA.