How do I relearn an entire course?

I know SAT Subject Tests were due today, but apparently, I’ve been waitlisted for bio, so I can’t use my fee waiver and have to pay $91. Can’t do that, so now I have to take it in October and relearn the whole course. How do I make sure I can go about this and still get a good grade? Also, how do I juggle relearning with my normal schedule?

Can you take it in August?