Indy gave great advice, I would only add that there are a few spinning instructors out there who like to "mix it up" by having people get off of the bike during class and doing pushups or something like that on the floor. If this happens please feel free to stay on the bike and keep pedaling - you don't have to do that.

We have two instructors who do that - which I do not understand - but I don't have to go to their class

Congratulations, that was a great gift!