Show addon in Tool Shelf - simple newbie question

How do I show an addon tab in my toolshelf? I downloaded a .blend file but it does not show the AddOSC addon tab in my toolshelf. I want to show it. I know that the author of this .blend file was using AddOSC.

You can see that my default startup Blender shows the tab properly.

I have tried turning the addon off, closing and reopening the downloaded .blend file and re-enabling the addon.

I have tried googling for 2 hours on Blenderartists and Youtube but I cannot see how to turn tool shelf tabs on and off for installed addons.

Thanks very much for any help or links to something that explains how to do this simple task.

Using 2.79 on Windows

Screenshot of problem:

hi eynet, would be nice if u shared the fileā€¦