This article explains how to connect a router to the internet. The instructions apply broadly to all routers and modem-router combinations.
How do I set up a router? | Internet setup
Once you have a subscription with an Internet Service Provider (ISP), follow these steps to set up your wireless network and connect to the Internet:
Connect your modem to the wall using a coaxial cable (the cylinder-shaped cable that screws into the wall and is used for cable TV) or a fiber optic cable if you have fiber optic internet.
Insert an Ethernet cable (one should have come with your router) into the WAN/uplink port on your router. The WAN port may be a different color than the other Ethernet ports.