The fifth Monday of the term is tomorrow, which means it's your last chance to add or drop a course. You'll need the instructor's permission to add (but not to drop) a course, and you'll have to pay a $10 fee—still, if you're currently in a class that's driving you crazy, consider it a small investment for your sanity. You can also just change the course's grading status to pass/fail, which won't incur any fees.
Any and all forms will require your concentration adviser or sophomore/freshman advisor's signature. Get them in by 5 p.m. to the Registrar's Office!