Most routers can be accessed using a web browser from any device (computer, smartphone, etc). Log in to the router when the prompt appears. If you haven't logged in to your router before, you will need the default login credentials.
If your router comes from your ISP, check with them for login assistance. If you purchased your own router, check with the manufacturer.
Each router manufacturer has a unique web interface, so the exact location of the settings we need to change will vary between devices. Look through the menus for Channel settings; it can usually be found in the Wireless settings section. And in some cases, you may need to look under Advanced settings.
Once you've located the channel changing options, take note of the current settings. When you're ready, adjust the Wi-Fi channel to reflect a new value. You may need to experiment to find a frequency without interference.
If you can't find the appropriate settings or are unable to change the channel, check with your ISP or device manufacturer for support. Check their website for any online troubleshooting guides or walkthroughs on the channel changing process.