Professional staff and student tutor walk-in hours are the primary source of tutoring. Walk-in hours can be very busy. You may get the help you need in just a few minutes. But if you have several questions or lots of work to do, you should plan on at least an hour. A walk-in tutor will probably work with you part of that time, and check with you periodically.
Appointments are usually for an hour.
A study partner is is always welcome.