Commodore 64/VIC20 games on PS3 Retroarch

I have a CFW PS3 with Retroarch installed, I play Sega & Nintendo roms on it and they run perfectly, However I would love to play old Commodore VIC20 & C64 games on it. Can anyone explain how I can do this, I know I need to install an emulator into Retroarch, but Im new to this Emulation thing and unless it comes pre-installed im useless, So a good easy to understand guide to installing a Commordore VIC20 emulator into Retroarch on a PS3 would be very very much appreciated…