Qt5Package for VS2015 - How to convert existing project to Qt project?

I know this isn't an official tool created by the Qt team, so apologies if this is in the wrong section.

I'm using the Qt5Package extension for Visual Studio 2015 as the official Qt Addin doesn't work on versions above 2013. I'm attempting to convert an existing, non-Qt project into a project recognised by the Qt5Package extension. According to this StackOverflow answer, right-clicking on an existing solution should provide an option to convert to a QtAddin project; however no such entry appears. Image of what I see:

Attachment 12055

Any help would be greatly appreciated.

Do this on project not a solution.