I have come across this custom widget,
https://github.com/akontsevich/WidgetBox
however I am unable to work out how to use it in my current project.
I have tried including the files in my project, as well as including a .pri file in my project.pro but it won't.
How do you use custom widgets, (this one for example) in a project?
You've got two ways to work with that. First look at the project file for the widget: WidgetBox pro. Notice the lines:
TEMPLATE = lib
...
creator_target.output = WidgetBoxPlugin.dll
This means you can build a library from the project and use it inside yours (after including proper headers)
Another way would be to include all the sources from the WidgetBox project into yours and build them along with your source.
Which approach to use depends on your needs. If you don't plan to modify the widget building it once from the authors project should be enough for you.