Things You'll Need
Instructions
Download WinRAR and install it on your computer (see Resources).
Run WinRAR and use it to unpack your RAR theme files. While the program is working, plug your PSP into your computer with the USB cable and set it to "USB Mode" by selecting "USB Settings" from the "Settings" menu.
Open the PSP memory stick by clicking on its corresponding icon in "My Computer" and locating the "Theme" folder. Copy the unpacked theme files into this folder.
Disconnect your PSP from the computer and go to "Settings" and "Theme Settings" to set your new PSP themes.