Interact with Visual Studio for Mac as follows:
Visual Studio -> Extensions -> Gallery -> IDE Extensions -> "VIM" -> Install
Then close the current document that you are working on and open a new document to activate the plugin. If that doesn't work, restart Visual Studio
Check the release page as there is usually a more recent version of the addin here than on the Visual Studio for Mac feed. Grab the .mpack file and install it via Visual Studio -> Extensions -> Install from file
Jump in our Gitter channel and introduce yourself.