The Sony PlayStation Portable can have custom firmware installed on it in order to open up features like playing your disc-based games from the memory stick. In order to install custom firmware, the PSP needs to first be placed into service mode. Usually you would use the Pandora battery for this task. But another product exists that can also place the PSP into service mode.
Turn off your Sony PSP and remove the battery and memory stick from the device.
Insert the Magic memory stick into the PSP. Insert your Datel service tool into the PSP battery slot.
Wait as the PSP is placed into service mode and turned on automatically. From here, install custom firmware or official firmware, or select "Exit" to shut the PSP down.
Reinsert the normal battery and memory stick back into the PSP, then turn it back on.
Installing custom firmware on the Sony PSP is legal but voids your warranty.