Apple AirPort Express v4.2 - Manual (Page 9)

Getting Started 9
Plugging In AirPort Express
Before you plug in your AirPort Express, first connect the appropriate cables to the
ports you want to use, including the Ethernet cable connected to your DSL or cable
modem (if you will connect to the Internet), the audio cable connected to your stereo
(if you will use AirTunes to play music from iTunes), and a USB cable connected to a
compatible USB printer (if you will print to a USB printer).
Once you have connected the cables for all the devices you plan to use, connect the
AC plug adapter if necessary. Plug AirPort Express into the wall. There is no on switch.
AC plug adapter