From within the project:
Click on the blue “Share ” icon in the top right of your screen, then select "Invite Collaborators."
Add the email addresses of the people you want to invite to the project
Add a message (not required)
Send the invites
The invitees will get an email inviting them to the project from you. If they have not used VeryBusy before, they will be asked to sign up and then brought directly into the project and asked if they would like a quick tour of the VeryBusy interface.