1: The GPC editor is pretty basic. If you don't know anything about programming webpages using html-code, just stick to it. Maybe Google will provide a more flexible page editor some day, allowing you more freedom of design on your pages. 

2: Using GPC there's this nice little button at the bottom-left of  the edit-page that says "Edit HTML". Click on it and you get too see (part of) the html code of your webpage. There's a number of things that you can do there. I shall try to cover most of these in these help pages.

3: The third way: simply forget GPC. Use any WYSIWYG editor (e.g. Frontpage) and design your own pages. You can upload these to your webspace. 

As far.