Where to find custom map files and transfer to updated game folder
You just need to drop the map into that folder.
If you are completely unsure of where this is:
eg. my current version maps are kept at \My Documents\OpenRA\maps\ra\release-20200503 since Im on windows and have older installsThe support directory is where the game keeps the saved settings, maps, replays, logs and mod assets. The default location is as follows, but one can choose to move it to an arbitrary location by passing an Engine.SupportDir argument to the Game.exe
macOS: /Users/<username>/Library/Application Support/OpenRA/
Older releases (before playtest-20190825) used different locations, which newer versions may continue to use in some circumstances:
Windows: \Users\<Username>\My Documents\OpenRA\