To add a static route, open command prompt and type the below (Amend the ip details as required). The below command is just an example.
route add 10.0.0.0 mask 255.0.0.0 192.168.0.1
You could also add the costmetric command. Assigns an integer cost metric ranging from 1 to 9,999 to be used in calculating the fastest, most reliable, and least expensive routes. If costmetric is not specified 1 is used as default.
Example of command with costmetric:
route add 10.0.0.0 mask 255.0.0.0 192.168.0.1 metric 2