[GS] How to change spawn points on a downloaded map?

[Stop_HmmrTime]

There are two maps that I've found that I'd like to play on, but I really need to make a few adjustments to them before I play with them.

The first map is this version of the world of Avatar the Last Airbender (link here: https://steamcommunity.com/sharedfiles/filedetails/?id=1785136128&searchtext=avatar) that I'd like to adjust. I'd like some more city-states and to change who spawns for each nation.

The second map is this map of the contiguous Lower 48 United States (link here: https://steamcommunity.com/sharedfiles/filedetails/?id=1910437393&searchtext=CONUS) that I'd also like to adjust by more rivers, moving the mountains around and making resources less scarce. I'd also like to play a game with a bunch of European civs and some extra city-states that come with the CIVITAS Expanded City-States (link here: https://steamcommunity.com/sharedfiles/filedetails/?id=1331757859&searchtext=civitas) to create a "Europe in America" type of scenario.

Any help at all is appreciated. I absolutely hate how complicated WorldBuilder is in this game. Thanks in advance.