I looked, but couldn't find guidelines for contributing maps. Presumably they're here somewhere and I'm just not spotting the link.
Thanks
Installers here:
http://www.gpsfiledepot.com/tutorials/how-to-create-garmin-topo-maps---part-9---compiling-data/
Once you are ready to upload click on "your account/files" at the top right of the screen and "manage maps/add a map".