With the macro(s) in your presentation file you can now use it in that file or with any other PowerPoint file you have open. Bear in mind that to use your macros, the file that contains them must be open. You can add as many modules and macros as you like in a PowerPoint file so you could create your own library of macros in a single file that you then access from all other decks. When you have multiple PowerPoint files open, make sure you select the file that contains your macros in the Macro window by clicking the Macro in drop down: