Preferably with a LAN cable connected device, sign into the Wireless settings here. Use admin as the password. Click on Advanced Setup, then Wireless. There you can specify the channel you would like to use for whichever WiFi band you're using. Be sure to click "Save Settings" at the bottom to save your changes.
Edit: Keep in mind that if you make the adjustments while connected via WiFi, you'll at least temporarily lose your connection after clicking "Save Settings". Also, if a change is something your device doesn't "like", you may lose the connection altogether, which is why a LAN cable connected device should be used when adjusting any WiFi settings.
Hope this helps. 🙂