How Do ?

I get any roms to play on my psp? i'm new to this i have no clue what to do please someone help.

What kind of rom? You'll need a certain emulator and a PSP with custom firmware if I'm not mistaken.
Go here and look on the sidebar and scroll down for a huge list of different emulators.http://psp-news.dcemu.co.uk/

n64 roms like the legend of zelda ocarina of time and majora's mask wwe no mercy

Well go on the site I suggested, look on the sidebar and scroll down to Emulators and look for Nintendo 64 then try out one of those emulators there. Try finding the official site since most of the emulators aren't updated.