You are able to set up several Lifekey devices associated with your account:
Setting up another Lifekey device under the same profile
If you want to set up a device on an existing profile, all you need to do is go to the scan page in the Lifekey app, and scan the new device. The app automatically detects a new device, and asks if you want to assign it to an existing profile
Setting up another Lifekey device with a new profile
If you want to set up a new profile, first click on the profiles tab in the Lifekey app. Next, either create a new person or pet profile. Once the new profile has been created, simply scan the new Lifekey device and assign it to the newly created profile.
(To connect with another user, you'll want to send them an invite from the "Following" tab. This enables them to receive updates when you tap and visa versa.)