NEED HELP WITH TEMPLATE TAG!

This is the 5th topic that I am forced to start on this topic. No one seems to know the answer to this problem. My blog (www.rusnarod.com) doesn’t display the author’s names or nicknames in the posts. All it shows is the date. I want the posts to also show the authors next to the date.

I found a template that that is supposed to fix the problem…but I have no idea how to install it or what to do. Can someone please tell me what I need to do? Here is the template tag I am talking about:
https://codex.www.ads-software.com/Template_Tags/the_author

Thanks You!!