creating an .xml file

use a plugin. ?? Its beyond the scope of this forum to explain the syntax necessary.

https://www.google.com/search?hl=en&q=wordpress+sitemap+generator+plugin&btnG=Google+Search

Thank you, I appreciate it. I know just enough to think I can put everything together how I want it, but not enough to do so without help!

You need to use some developer tools such as this one here:

https://www.stylusstudio.com/xml_generator.html

This package has a free seven day trial which will allow you to create a fully compliant .xml file to work with this plugin. Then once you create sitemap.xml, copy it and create sitemap.xml.gz with your standard gzip tool.

https://www.gzip.org/

Hope that helps.

– nina

Try Google XML Sitemaps, a plug-in. You can use that a couple of times to see how it formats the XML, etc. and then go it alone if you wish.