Instructions
Select the "PSN Store" icon on the far right of the PSP main menu.
Select "Themes" from the store's main page to see the list of available themes for the PSP. Select a theme, and choose the "Add to cart" option. The theme will automatically download and install on your PSP.
Press the "Home" button on the PSP, and select "Yes" to return to the PSP main menu. Select "Settings" from the main menu, and choose "Theme Settings." Select "Theme" to see a list of installed themes.
Select the theme you downloaded, and select "Apply" to use it on your PSP. The screen will shut down and turn back on to apply the new game boot.