The proper, accepted way to install a mod is to put it in your MODS directory. I tried to get it to work in the MODS directory, but for some reason it won't. It works in the CustomAssets directory, though. Just stick the 2 files in the customassetsxm
To go with the Gigantic Map mod, I've created a mod that slows down the game even further than the Epic setting. I call it Dynastic. It also significantly extends the total number of turns in the game.