First day's nothing to worry about. Check out the syllabus, see what's involved, and see how the professor is. If things look like a mess (within reason, as every class is going to have stuff lined up for you to do), just drop the class and swap it out for something else that you still need to take.

It's really just a matter of staying on top of it. Go to as many classes as you can, and if you find yourself missing one, just reach out to the professor and ask about what was covered so you don't fall behind. No worries. Good luck and all the best. :3