I have done with setup and all n everything is proper but still I am not able access my server through rdp

You may follow the instructions at https://www.dynu.com/Resources/Tutorials/DynamicDNS/RemoteDesktop to check if port forwarding and firewall have been set up correctly.

One thing to note is that you need to be outside of the network that your server is in. When inside the same network, you need to use the server's internal IP address (192.168.0.X) to access it since router does not allow bounce back traffic.