First run the telnet program and tell it the IP address of the router through the Run command on the Start Menu by typing telnet xxx.xxx.xxx.xxx Replace the x's with the IP address of your router. The default address is 192.168.7.1

When you click OK you will get the window shown below:

You need to log in to the router with your Username and Password. When you type in your password, it will not display it, so just type it and hit enter.
You will then be logged in, and will have a $ prompt.

Now all you have to do is type in the commands at the $ prompt.
When you are done with your changes, remember to commit them by typing in the command commit, then type quit to exit.