Hi Mark
The example you are looking at is very old, not only is it for Kentico 8, but it is using Portal Engine and you're trying to use MVC.
Do you have a Controller and View set up for this page?
If so, you will need to retrieve the list of categories in there - I would recommend using DocumentCategoryInfoProvider.GetDocumentCategories(documentId)
to retrieve the document categories.
Pass this data in your view model to the View, and output the data in there (looping over the items in the list).