If the add-in doesn't show up in the "Home" tab after you've installed it, or if it disappears after each restart, please make sure that starting web add-ins is allowed. To do this, go to the trust center settings:

Then go to the "Trusted Add-in Catalogs" tab. Make sure both of these checkboxes are unchecked:

Now restart Word and the add-in should appear. Depending on your version of MS Word, it might be hidden behind an icon with three dots ("...").