Instructions
Firmware Eboots
Download the official firmware update from the Sony website and save it to your computer.
Connect your PSP to your computer with the mini-USB cable and open the contents of the memory stick.
Create a new folder called "UPDATE" in the "PSP/GAME" folder on the memory stick.
Copy the firmware "Eboot" file you downloaded from your computer to the "UPDATE" folder on the memory stick.
Disconnect your PSP from your computer and connect it to the AC adaptor. Do this to ensure that the PSP remains charged while the update installs.
Start the PSP then scroll to "Memory Stick" (found under "GAME" on the main menu) and press "X." Press while the "PSP Update" is highlighted to begin the installation of the "Eboot."
Games and utilitiy Eboots
Download the homebrew utility, emulator or PlayStation One game eboot file that you want to use on your PSP that has custom firmware installed.
Connect your PSP to your computer with the mini-USB cable and open the contents of the memory stick.
Create a new folder inside the PSP/GAME folder on the memory stick. The folder should match the Eboot file so for example if you are installing a "SEGA Emulator" name the folder PSP/GAME/SegaEmu or something similar. It makes no difference to the PSP but will make it easier for you to keep track of what's installed on the memory stick.
Copy the Eboot file you downloaded from your computer to the newly created folder on the memory stick.
Disconnect your PSP from your computer then start the PSP and scroll to "Game" on the main menu. Highlight "Memory Stick" then press "X" and a list of all the Eboots installed on the memory card will be shown.
Highlight the Eboot utility, game or emulator you want to load and press "X."