If you're using Windows, you will need to have Bonjour installed for Composite to work. Please see Bonjour on Windows for help installing it. If you're on OS X, Bonjour is already installed. For Remote Connections to be available, you also have to make sure that you have Photoshop version 12.0.4 or newer.
Setting up remote connections
In Photoshop, open the edit menu, where you will find Remote Connections:
Turn on Enable Remote Connection, and choose an appropriate Service Name and Password:
Now, when you open Composite and you're connected to the same Wi-Fi network as the computer running Photoshop, you should see an available connection with the name you specified.