You will want to do the following with Word closed.
Go to the folder “[Hard Drive Name] : Library : Application Support : Microsoft : Office365 : User Content : Startup : Word” Note : If you have trouble finding the above location you need to click on Finder (in the Dock the icon of a face) to the right of Finder click on the Go menu then click on Computer then click on the Macintosh Hard Drive. You should then be able to follow the path above. Note: In non-English versions of Word, the folder named “Startup” may be called “Start” or be in the localized language of Word.
You will want to delete any EndNote file in the folder listed above. Once the file has been deleted then reopen Word and EndNote should not load into Word anymore.