Hello,
How to configure an Airport Extreme Router
Power on the AirPort Extreme Base Station by plugging it in the wall.
Open the Airport Utility app.
In the top left of the AirPort Utility dialog click on Other AirPort Base Stations or Other Wi-Fi Devices.
Click on the Airport Extreme that is listed. ...
Click Next.
Thank You.
Airport Extreme Setup
Apple Airport Extreme Setup
Setup AirPort Extreme