To link a document to a template:
Open a document to which you want to attach the template.
Go to the Developer tab on the Ribbon.
Click Document Template in the Templates group.
At the top of the Templates and Add-ins dialog box, click Attach.
Locate and select the desired template. (This links the template to the open document.)
Then click Update document styles. (This updates the styles in the document according to the styles in the template immediately (after you click OK) and the next time a user opens it -- if the user has access to the template path, i.e., it's in the Templates folder on their computer or in a workgroup templates folder on a network share.)
If you want to control when the user documents are updated, after clicking update styles and clicking OK to save the setting and update the styles, open the Templates and Addins dialog again and uncheck the option.
I have no expeience with master documents, so I can't address that question. Hope this information gets you one step closer.