There are 3 ways you can invite contributors to a Bubble.
1. When Creating a Bubble:
2. After you have created a bubble: go into your Bubbles tab --> Select a Bubble --> Click Members button (Pictured below) --> Insert new members email address
3. Inviting with a Bubble Pin: Follow step 2 (found above) --> find custom Bubble PIN in Members section --> Copy PIN and share with New Members