In general, default settings of wifi device for the channel is set to automatically, when there are existing wifi signal, the new wifi device will seek and occupy unused channel.
But just to be safe if you are confident in your area has wifi signal and you will install the new one, the channel should be set up manually. to avoid interference between the devices.
Channel menu on wifi device generally will be found in Wireless section, refer to your device manual instruction.
The easy way to know wi-fi channel already used in the area, I use Wifi Analyzer, the App for Android. Easy to use and has good measuring result.
Take your Android device, go to Play Store, search using keyword: Wifi Analizer , choose the Wifi Analizer from farproc with the logo: