fat psp version 3.72 ... how can I install custom firmware?

I updated my psp to version 3.72

but i really want to play iso/cso games from my memory card
and i understand you need custom firmware for that ...?
can someone show me how to do this?

do I have to downgrade?

I have fat psp and i'm not sure what to do?
I tried creating pandora battery but it keeps telling me

the game could not be started
(8002014C)

and i tried installing 3.72 HX-2
it tells me i dont need to update

what should i do now?

I read that part but i dont know any one who has homebrew psp ...

There is this one site Dark Messiah, it has a list of people that can do this for you.