how do I load skins?

Hello, I love this forum. I have one going here http://www.louisekennedydesign.com/forum/  I just uploaded new avitars yet they don't show up when I tried to edit the profile, although I can see them in the avitar folder on the server.

But my question is how do I change the colour of the pages. I uploaded the olive skin in forum-images, but it only changed the icons (I took them off because the images were not as clear as the default icons). But I want to give all the pages a new background, instead of white. How do I do that?

thank you!