How can I play emulation on my PSP?

I’ve heard so much about how people modify their PSP to play SNES and NES games, but how exactly? You can’t collaborate different button schemes, can you?

http://www.google.com/search?hl=en&q=emulators+PSP+FAQ

4th result:
http://www.informit.com/articles/article.asp?p=415794&seqNum=3

That wasn’t so hard!!

This is actually against the rules.