This must be done in bluetooth range of the Keybox with Bluetooth and Internet connection.
1) Tap on the menu icon on the top left hand corner of the app
2) Tap on 'Set Up Home'
3) Select your Keybox
4) Tap on 'Manage Locks'
5) At the 'List of Locks', tap on the rubbish bin icon, then tap the red 'minus' logo beside your Keybox name.
6) Ensure that your phone is near the Keybox (less than 1m)