Word 2016 documents, including blank documents that use the Normal template, are associated with a template. If you choose the wrong template or suddenly desire to change or reassign a document's template, follow these steps:
Open the document that needs a new template attached.
Click the File tab.
On the File screen, choose the Options command.
The Word Options dialog box appears.
Choose Add-Ins from the left side of the Word Options dialog box.
Choose Templates from the Manage drop-down list.
You find the Manage drop-down list near the bottom of the dialog box.
Click the Go button.
The Templates and Add-ins dialog box appears. You should see which template is attached to the document, such as Normal.
Click the Attach button.
Word displays the Attach Template dialog box, which looks and works like the Open dialog box.
Select the template you want to attach.
The templates listed are stored on your computer, so you don't see the full range of templates that you would find on the New screen.
Click the Open button.
The template is attached to your document.
Ensure that the option Automatically Update Document Styles is selected.
Updating styles means that your document's current styles are changed to reflect those of the new template, which is probably what you want.
Click OK.
The styles stored in that template are now available to your document, and the document is now attached to the template.
Note that attaching a template doesn't merge any text or graphics stored in that template. Only the styles (plus custom toolbar and macros) are merged into your document.
You can also follow these steps to un-attach a template. Do that by selecting Normal (normal.dotm) as the template to attach.