re: How to become a member of a collaboration ?

Rose most collaborations are secret until they are revealed. The person heading up the collaboration asks people to join them. They use Facebook and have a secret group to communicate. There is a group on Facebook that hosts a lot of collaborations https://www.facebook.com/groups/CPCcollab/

You could also just start your own collaboration by coming up with a theme, pick cake artists to join you, and pick a reveal date.

Jennifer, https://www.facebook.com/PrimaCakesandCookies