Instructions
Turn off your PSP by holding the sliding power button up for five seconds.
Hold the "Right" trigger button on the PSP and turn on the PSP by sliding the power button up, but continue to hold the trigger button. You will be presented with the PSP recovery menu.
Select "Registry Hacks" from the PSP recovery menu. You will see the "Activate Flash Player" option.
Select the "Activate Flash Player" option from the recovery menu and select "Back" and "Exit" to reboot your PSP. When the PSP boots into its menu, Flash will be activated.