Visual Studio 2015 generate UML from code

I have a almost finished project and now I need to write a documentation. I found some information in the www which tells to "simply" generate UML from the existing code.

At the top Menu is a section with and there I can create UML diagrams, but I can't import the classes which the project have. In all the other forum entries they was talking about a where you can simply drag and drop the needed classes and the dependencies are automatically created, but in my case this view is missing.

If you have some good advise how to document the software differently, you're welcome.