This guide refers to a Rosewill RNX-EasyN4 router, but will apply to most Rosewill routers in general.
1. Access the router's browser-based utility.
Log into your router’s browser-based utility by entering 192.168.0.1 or your default configuration IP into a browser. The default username and password are both admin.
Enter 18.104.22.168, 22.214.171.124 respectively in the "First DNS Server" and "Secon DNS Server" fields.
To save your settings click on the "Apply" button.