I’m new to the vassal system how do I find groups who play the GMT coin games?
You might have done this already, but … Decide on a game, say “Cuba Libre”. On the VASSAL website go to modules, C, Cuba Libre.
Near the bottom of the module page there’s a list of players (at least for some games, including “Cuba Libre”). There is also an “Opponents Wanted” forum, but I don’t know the details. I haven’t done very much with VASSAL, so I don’t have much more to offer.
BTW, for other people reading this, “coin” means “counterinsurgency” here.