The setup process is incredibly simple and entirely app-controlled. Load the app on your mobile device or computer and it will automatically scan both the Wi-Fi network you’re currently on and any Chromecast sticks in “Setup” mode. Tap the stick in Setup mode and enter the password to your Wi-Fi network (the app will automatically fill in the Wi-Fi network you’re currently using). The Chromecast will automatically connect to your network, and it will show that it’s connected (and the strength of the Wi-Fi connection, and the assigned name of the Chromecast).
Your streaming content choices are currently limited, though Google released an API for the Chromecast, so more apps could support it in the future. From an Android device, you can stream media from Google Play Movies and Music (in a limited way, explained below), as well as Netflix and YouTube. From an iOS device, you can watch Netflix and YouTube via the Chromecast. From a computer (Windows or Mac OS X), you can stream media from Netflix, YouTube, Google Play, and Chrome (streaming the view of an active tab to the Chromecast). These apps all get their own Chromecast buttons when the Chromecast app is installed and your Android device detects Chromecast sticks on the network. In supported apps, streaming media to Chromecast is as easy as streaming through AirPlay; just load the media, tap the screen icon, and select the Chromecast to which you want to stream.