Super Confused, but maybe Not? The new DUCKDNS

Hi, I hope this might make sense and thanks in advance.

Am I correct by saying that there is no need in the latest DuckDNS add-on to follow the installation steps on the DuckDNS website for a Pi3? The new add-on has Let’s Encrypt providing you make the terms true and put in your token you get from the Duckdns website. I guess what I’m asking is, I can get to my sub domain called “my-domain.duckdns.org” (obviously my-domain is changed to the name I chose) which takes me to my routers main page from anyone’s PC or phone browser. I logged into Xfinity router and they make you go to some new site to do a port forward. When I do that I forward port 8123 from the internal IP address of the Pi which by the way is static because I made it that way on the router. Then I add the 8123 at the end of the duckdns domain…like above, and it times out. Does that mean port forwarding does not work? Or do I need to go through some of the longer installation methods of logging into the Pi terminal and doing all the sudo code that I have no idea what it really means. Thanks to all of you, you have made it more easy for people like me that want to learn. I hope that is the case…that the new add-on is that simple. I get no errors on the duckdns log from the add-on section. It always says a time/date and then an OK and then the WAN ip, then it says NO CHANGE. No errors.
I can run the home assistant from the https://xx.xx.xx.xx:8123 (x’s being the static IP of the Pi running home assistant. My web browser does say its not secure which might be another problem.

Thanks so much for any help…

You will want to forward 8123 external to 8123 internal… or 443 external to 8123 internal and you will just use https:// externally without port number.