Instructions
Turn off your PlayStation Portable. The off button, on your PSP, is located on the right edge of the PSP.
Take off the back. Expose the used battery by simply sliding the left piece of the back cover off.
Take out the battery. The battery might be a bit stubborn, because it fits into the PSP like a puzzle. Use a tool, such as a butter knife or a key, to pull the battery up and out of the PSP.
Place the new one into the PSP. Like before, the new battery will fit into the PSP like a puzzle piece.
Re-cover the PSP with the unattached cover and turn on the PSP.