1) When typing the collaborators name, if they are already a member of pressbook then their name will appear in a drop down.
If you see their name, please select it from the list, otherwise continue typing their name and enter email(optional, but preferred for confirmation)

2) Please select the profession from the offered list, or enter your own description .(optional)

3) Please select from the different classifications; Client, Team/Collaborator, Supplier, Contact/Agent

Thanks,
Pressbook support team.