You need to create users and channels by using your admin web console. Then launch the app and login with a ZelloWork account.
If you run ZelloWork on Android, Windows Mobile, Blackberry, or Windows PC, make sure to download clients directly from the homepage of your network.
ZelloWork is available for iPhone and Windows Phone as well. You need to download Zello iPhone app from App Store or Zello Android app from the Windows Store and use the ZelloWork account option to connect to your network.