Add domain bought at Noip.de?

I hosted my own Minecraft server and would like to add a purchased domain, at noip.de there are only other free ones and now I would like to know how to add a purchased domain there, can anyone help me?

Is described here:

https://www.noip.com/support/knowledgebase/can-i-use-my-own-domain-name-with-no-ip/

Depending on where you have registered your domain, your provider may offer its own DynDNS service. So I would look there first