N00bs, ok listen up. We don't support you on downloading roms at this forum. On how to run a rom in Generator, that's a different story.
After you downloaded a rom from the internet. Unzip it to where you extracted Generator e.g. x:\Generator (X means that it can be any drive letter) then you go into dos prompt mode.
From there go to you generator folder and type out dosgen *.smd (* would be the name of your rom)
But that's Dos, if you got linux then I'll won't be any of use for you.