The General GRE test itself is registered separately from Mark’s course. You can get information on aspects of the GRE General Test from the ETS Company at ETS.org/gre or gre.org. You can book a test on this site and take it at a Prometric Test Center closest to you. 1-800-GRE-CALL is yet another way to set up a booking.
Remember: you can choose an individual time and date for your GRE test taking. The fall is the most crowded time and it is well to grab a place as soon as possible; otherwise you may have to go to another farther away center. Be good to yourself: if you find yourself too rushed after scheduling you can reschedule up to within 10 days before your test date, for an extra fee of course. (But still worth it if you find you are not psychologically or mentally quite positioned for the test yet.)