This is a very simple tutorial for new ps3 owners since they are gradually coming.

1) Go to your ps3 web browser

2) Navigate to PS3 Themes (Website)

3) Find a theme. Click Download Here, and save it it will install for you.

4) Go to Settings, Theme Settings, Themes and select the theme you just installed and press "Apply"

Hope I helped you new ps3 owners or oldtimers who never explored the theme world.