The instructions are pretty much spelled out for you on the device itself. Try again later, or connect to iTunes to activate the device.
You can use any computer running the latest latest version of iTunes in order to activate it. You can take it to an Apple Store and ask them for help.
You could also try using another WiFi Network or power cycle your modem/router. Unplug it from power for about 30 seconds and then plug it in again.