Go into the router admin settings, and look for the devices list. You will have to match the MAC IDs listed there to your SW radio device, but there you should be able to see the IP address assigned by the router.
Usually, your router will be at 192.168.1.1. Go to that address with your browser and you should get a login prompt. If that does not work, try 10.0.0.1
If either of those dont work, you will need to reference your router information to determine what the ip address of the router is and the login information.
Once you get logged in, you can probably reserve that ip address via the settings where you see the devices connected as @FlavorfulTreat explained above.