Instructions
Check your PlayStation Portable's firmware. To use your PSP as a PlayStation 3 controller you have to have firmware version 3.0 or later. This can be checked in the "Settings" menu on the main screen of the PSP. If you need to upgrade, you can do so by going to Sony's U.S. PSP website.
Plug one end of your USB controller cable into the USB jack on the top of the PSP, and the other into any controller port on the PlayStation 3. This will make the physical connection between the two units.
Make the appropriate changes to the settings of your PSP. You can do this by selecting "Settings" and then "USB Connection." This will put your PSP in "USB Mode," which is required for interaction with the PS3.
Register your PSP with your PS3. You can do this by selecting "Remote Play Settings" from the Settings menu on your PlayStation 3, and then selecting "Register this Device." This will allow the software on your PSP and PS3 to function together.
Select the "PlayStation 3 Network Connection" on your PSP. This screen can be accessed by selecting "Settings," clicking "Network Settings," and then finally selecting the connection that reads "PlayStation 3." This will make the final adjustments and allow you to browse videos, photos, the internet, and control the music library from your PS3 all using your PlayStation Portable.