go to a different class if a certain variable is set to 1, how would I do this?
I'm confused on this, you don't really jump or "go to" a different class, classes just perform various procedures if you have methods inside of them. You have an entry point, which calls a new instance of, by default Form1, and this is where your application runs.
If, in the settings you configure it to close upon the last form, or when the first form closes, it's possible to close the form associated with the initial startup form and run code only in the next form, lets say called Form2, but typically all other classes just run code for you, simultaneously while your main Form code still runs in the background; listens for events, etc...
Instead of explaining what your problem is, and especially since you're just starting out, lets go with something a bit more appropriate so we can help you out: What are you trying to achieve?
I ask this because most of the time, the user has an issue, and because they don't truly understand how they should be doing what they are trying to do, it's either an odd way of doing it, or it's wrong.