which mod? Just put the mod in the same place you go to start the game, so for example if tpt is located in a powdertoy folder inside of My Documents, then that's your tpt folder and just put the mod's exe and all the dlls with it in that folder. If you put it in your tpt folder, that just allows you to use the stamps you have been using from normal tpt (maybe you want that), but it isn't too important

Then you don't have a tpt folder, you just keep tpt on your desktop. Put the mod there too. To run the mod, just click on the .exe. It doesn't need to be installed, or even need the real tpt to run.