I’m assuming you’re on a MAC but if you’re on PC you can do the same from command prompt
Go to Utilities > Terminal
type in ipconfig and press Enter.
The Default Gateway will show the address you need. It should look something like this: 192.168.0.1
The default login is usually admin for both username and password, however can vary by model.
Depending on the model the login to the router might vary, but here’s the general idea…
Find the router ip and enter it in a browser’s address bar (most common 192.168.0.1 or you can find it through command prompt).
Login to the router (usually admin for both username and password)