Hello
I have router Huawei model :B135s -22.
I'd like to know how to configure my router for dynamic DNS service. I'd like to use dynamic DNS service for remote desktop.
Thank you.

Check if your router DDNS provider has option for 'dyndns-custom'. All lastest Huawei firmware should have it. Use the following:

Service Provider : dyndns-custom
WAN Connection : nas_0_38
Host Name : api.dynu.com
Server port : 8245 or 80
Domain Name : If you have a Dynu subdomain yourdomain.dynu.com, enter yourdomain.dynu.com . If you have your own domain name yourdomain.com, use yourdomain.com .
User name : your Dynu username
Password : your Dynu password, IP update password or MD5/SHA256 encrypted password

To set up remote desktop, you will also need to set up port forwarding for port 3389 in the router. You can follow the tutorial here.

P.S. in case that your router does not support configuring DDNS, you can always use a free IP update client. The drawback with an IP update client is that you have to keep the computer on. If you are using DDNS for remote desktop, your computer will be on anyway so you might as well run the IP update client on it.