Usually, it is easy, but some internet companies make it hard to set up without their own routers; please try the following:
Please connect the modem to the router's Internet/WAN port, the computer (use the only computer that works if connected straight to the modem) to one of the router's Ethernet/LAN ports, and the power adapter to the belkin router device, then reset the router: make sure the router has power, then use a paper clip to press & hold the tiny reset hole/button located on the back/bottom of the router for 10 seconds. Then wait a few minutes.
Next, on that same computer, go to the router's login page at http://192.168.2.1
and click Login
in the upper right-hand corner of the page if available. The router does not ship with a password, so just click Submit
when prompted. Then look around for the option to clone the router's MAC Address with the PC's MAC Address, then save, then wait a few minutes and check Internet.
Please let me know if there is still any issue. Thank you.