Instructions
Turn on the Sony PSP Slim and select the "PSN Store" icon from the far right side of the PSP Slim XcrossMediaBar (XMB) menu. The PSN Store homepage will appear.
Select the "Themes" section of the PSN Store homepage and you will see a list of available themes for the PSP Slim. The theme will change the icons, colors and gameboot of the PSP Slim.
Select a theme that you want to apply to your PSP Slim and select "Add to cart" from the top portion of the page that appears.
Select "Checkout" and you will be brought to the purchase page. While many PSP Slim themes are free, there are a few that aren't. If you need to pay for the theme, enter your payment information, credit card or PSN card number, and select "Yes" to complete the purchase. If the theme is free, simply select "Yes." The theme will download and install.
Press the "O" button on the PSP Slim and select the "Settings" icon on the far left of the PSP Slim XMB menu. Select "Theme Settings" from the list that appears, and select "Theme." A list of themes will appear. Select the one you want to use and select "Apply" from the right side of the page. The new theme will be applied, and your PSP Slim gameboot will be changed to that of the new theme.