In the app: press "Share a key".
1, Cross of for the door(s) you want to share keys to. 2, Select recepient(s) from your contacts or via phone number. 3, Set the duration of the key, either immediately or in the future. 4, Cross of if you don't want notifications when the key is being used. 5, Add a message (optional). 6, Lastly, press "send keys".
Keys shared from the app are personal, trackable and can't be shared further.