At the top right hand corner of the editing page is a link that says "Change Look", click on this link. On the next page you will see a whole lot of different looks you can use on your Web page. They come in different colors, different layouts and different styles. Pick the one you think you like best for your Web site.
When you have decided on the look you want for your page click on the "Select" link under the picture or on the picture itself. You will be brought back to your editing page but now you will see the new look show up so you can see what your page will look like.