Tutorials are all by appointment.
First you need to register. The Centre co-ordinators will assign a tutor to you, and the tutor will contact you to arrange a time. From then on, whenever you want to book a tutorial, you should contact your tutor directly by e-mail. If your tutor's timetable turns out to be incompatible with yours, you should contact the Centre Co-ordinators to get a different tutor. It is also possible to make appointments with a different tutor, but you should try and stick to one tutor, because it's less confusing for everybody involved.