It sounds like you are trying to access the mod configurations when you have already launched the game. I have never tried to do this since I don't know how changes will affect an already-running game. I know that R2Modman is super easy to use if you make changes after you've launched the mod mgr - before you launch the game. Also, the creator states that you can reach him with problems that you can't resolve by letting him know on his Discord channel.