Every router has a setup process you have to go through. Some service providers give you a ready-to-fly router but you've chosen to change from that one so you need to go inside it to find what you need.
Connect to the router by ethernet cable to your PC and assuming that PC is running a Windows system, press the Windows key and R together. In the Run box that pops up type
cmd /k ipconfig /all
and hit the Enter key.
In the black form that shows up, look for the entry Default Gateway and note the figures in that entry. It will look similar to 192.168.0.1 or similar. That will be the address of your router and you need to open your browser and type that address into the URL address bar. Hit enter and you get to the router's...