Things You'll Need
Instructions
Insert the Magic Memory Stick into your PSP's memory stick slot with the PSP turned off.
Insert the service tool battery into the PSP's battery bay and the PSP will turn on automatically. If it doesn't, you can turn it on manually. You will see the custom firmware install menu.
Press the "X" button to install custom firmware onto your PSP. Press the "X" button again after the install completes. This will shut down your PSP.
Replace the Magic Memory Stick and service tool battery with the normal ones and turn your PSP on. It is now running custom firmware.