Apple AirPort Express v4.2 - Manual (Page 24)

24 Using AirPort Express
How to Set It Up
1 You must have an existing AirPort network created by an AirPort Extreme Base Station
or an AirPort Express. To share Internet access, the network must be connected to the
Internet. The base station that is connected to the Internet is called the main base
station and shares its Internet connection with your AirPort Express.
2 Use the AirPort Setup Assistant to extend the range of your network. (See “Setting Up
AirPort Express” on page 26.)
Both base stations share the Internet connection with client computers wirelessly, or
using Ethernet if the client computers are connected by Ethernet.