The best way to get started designing something you've never designed before is to look for one of the existing examples.  In the example browser (File->Open Example...) you can search for the type of circuit you want to design and see all the examples of that type.

If you're trying to design a simple filter you can also start with the Filter Synthesis Wizard (expand the Wizard node in the project tree and double-click on AWR Filter Synthesis Wizard).