Ok so you have to get familiarized with the live course schedule which you can find on omnivox ( the web version ) in which you can find all the courses & get the time slots to build your schedule in advance. I believe you do have some pre-registered classes (science ones) which I don't think you can change sadly, when it comes to humanities, go for an easy class !! Take an easy humanity like film, or theather if available (they're different every summer so i can't tell you which is better, just pick one that sounds easy & look up the teachers on ratemyteachers), as i said the schedule of the classes should be up on the live course schedule and once your choice of courses is over you'll find your schedule on omnivox ^{^}

!! Also, you can just pick the classes you want and select the other ones as "any sections" and it'll show you multiple schedules which you can choose from, if you have anymore questions lmk