I've just created an Add-In from some code I wrote. The original code is a private sub to run when certain cells are double-clicked on only one sheet.

My question is this: once I have added the Add-In to another Excel file, how do I get the private sub to run in the new file using the Add-In?
Right now, it is behaving like it doesn't exist, but I can see the code from the Add-In.