Hello Ma'am. You have not mentioned the name of the university nor have you added any tags to your specific query. Please be more specific from the next time and add tags from the next time for us to help you in every way possible. We are always here to help you with every query possible. In general, you will be asked by the university itself about the time you need to pay the fees. Normally you need to pay the fees while getting the allotment letter.