Hi fungranny and welcome to the avast family,
It's not clear where you're having problems -- can I assume you can start the program OK and the interface (Status screen)? If so, right-click anywhere on that and select Settings from the menu, and you'll find most of what you're looking for.
Most of the default settings are just fine, at least to start out with -- let us know if there's specific areas you'd like help with.
Best,
Mike