What am I missing for a simple ddns remote connection?

I've been beating myself up trying to establish a remote connection via a noip.com ddns address. Port forwarding is set up on my router and included in my DDNS http address as such: http://myddns.noip.com:8123

I'm having no success, but I just got the screenshot message which says it can be done, but nothing about how to do it?

I know I can get a subscription for cloud based remote access, but I'm totally new to HA, coming from Smart things, and still the proof of concept stage to determine if I really want to commit to HA.

First of All, Don't ever expose your HA to the World through an HTTP address, Always use HTTPS.
For this you should enable HTTPS/SSL on your HA

Secondly , well im not familiar with noip, but ANY domain name pointing to your Routers port 80 (HTTP), will be Overwelmed with attacks and traffic to an extend you Really don't want in your Network. ( even port 443 is a desirable port to scan for millions if not hundred millions Devices/servers around the world )
So either you have configured your "Setup" wrong, or you have "misunderstood" something
Try with https://myddns.noip.com(port something else , i.e :443 , which should be forwarded to your-ha:8123
HTTP is kind of (Not encrypted traffic) so i guess you already send your username and password to your HA over an unencrypted protocol ( PLAIN text , for everyone to read )
DONT

Use duckDNS instead. There are loads of tutorials on setting this up with HA. There is a dedicated app (add-on) and it comes with LetsEncrypt built in so you are not exposing your server on the internet unsecured.