The attached doc shows how it can work.
The simplest way to get a linked CC is to insert a CC via Insert>Quick Parts>Document Property> and choose one. This will give you a plain text CC linked to that document property.
You can step up a level by going to Developer>XML Mapping Pane>{select a schema like core-properties}>right click on an element eg title and choose Insert Content Control>Combo Box.
If you want to really get serious, you should use the tools provided by
Greg Maxey or
Graham Mayor