There are three ways to join a bubble:

1. The owner of a bubble can add you to the bubble and you will receive an email inviting you to the bubble.

2. If the owner of the bubble has selected to allow participants to invite others (under the Bubble Privacy Settings: see where this is when you are creating a new bubble on your phone, OR when you are creating a new bubble on the web) a bubble participant can also invite you.

3. There is a third way to join, but it is not used as often and that is the manual PIN entry for Bubbles. If you have a bubble’s pin, you can join a bubble with that pin without having been invited to the bubble.

Go to the My Bubbles tab --> click the Join Bubble button --> Enter Bubble PIN and click Join the Bubble in the top right corner 

Enter the Bubble Pin to join the bubble.

How To Invite Participants To A Bubble/Join A Bubble With A Pin