If you have 2 gouramus in a 5 gallon tank how do you get your gouramis to stop fighting?

Gouramis aren't really great fish to have together unless they have room to move around (e.g. at least 5 gallons per fish). Your tank is MUCH too small to have two gouramis, they're fighting for territory. If you don't want to return one to the fish store, then you should definitly just get a bigger tank. Unless you have dwarf gouramis, you should have them in at least 20 gallons. It also depends on what kind of gouramis you have. Some are more social and are more likely to school (dwarf gouramis, pearl gouramis) whereas others prefer to be top dog (opaline gouramis, blue gouramis). Good luck!