How can i play downloaded games in my psp???

hey, ive just bought a new psp, it has firmware 3.4, ive got only one battery and ive read in some blogs that i have to convert my battery into a pandora battery and then downgrade my firmware to 1.5, then all games will work???, in a NOOB in this, can anyone help me how to play iso games in ma psp, and they said i need a spare battery too boot psp, i cant understand anything, and if possible please give me step by step instructions on how to fix this, pleaseeeeeeeeeeeeeeeee……