Getting OSM into Mac Basecamp

I downloaded OSM generic routable (new style).gmap files that I would like to get installed only into Basecamp on my iMac w/OS 10.0.1 and NOT into my device. I also downloaded JaVaWa and JaVaWa Map Converter as I read in a few forums these are required. It appears that GMTK seems that it is meant to be used once maps are already in Basecamp. When I use the Map Converter, I get a message that says “This folder does not contain a TDB file”.

How in the world does one get these maps into Basecamp? And why can’t Garmin/OSM make it so that they are self-loading with a simple click?