Download the zipped file by clicking the download button above;
Plug the Memory Stick into your computer's USB port;
Create the following hierarchy of directories (one folder within another) on the Memory Stick: PSP/GAME/UPDATE (all folders in capital letters);
Extract the downloaded file and copy the file into the respective version of your PSP. Example: if your PSP is 2000 copy the EBOOT.PBP file from the PSP-1000-2000-3000 folder;
Paste the download file (EBOOT.PBP) into the last folder (UPDATE);
Connect the Memory Stick to your powered PSP and select the GAME options > Memory Stick by pressing the "X" button and then select the PSP Update ver . X.XX and finally the "X" button to perform the installation.