Changing content in dynamic sidebar

Hello all! I’m a newbie, so please forgive my ignorance. I’m using (what I think is) a nice theme for my printing company’s site (www.xpressprints.com – still under construction), and it uses a dynamic sidebar. I want to change a few things in the sidebar – for instance, I only want a space for the different pages, and a place for the shopping cart, and maybe some google ads at the bottom. How do I go about doing such a thing? Thanks!