You will go to http://<your dnsdyn.org domain you received>:<port number>
you will need to port forward that port on the router.
I use a different provider but my address is http://<username>.dnsdynamic.com:<port number>\
EDITED: Do yourself a favor and test to make sure you can access it locally (from a computer on your network) first. This way you know that the web gui is working and all of that is working. This way if the dynamic dns does not work, you know that it is just a problem from the internet to the router, as it works fine on internal devices behind the router.