To create a new quick part, go to the end of the document and create the content you want in it. Then select that content (hint: experiment with including the final paragraph mark or not) and choose Insert > Quick Parts > Save Selection to Quick Part Gallery. You name the entry and set Type = Quick Parts, and Category = Vendor and make sure it is saved into the template that I posted.
Some background reading that will be useful to you is
https://gregmaxey.com/word_tip_pages..._autotext.html and
https://support.office.com/en-us/art...c-98599f16cadc