User

If you click the combo box of a User type field you will see a list of all users in your organization who are authorized to read this teamboard.

If you miss a person there ask the user who has Authorize rights for the teamboard to add this person at least as a teamboard Reader.

Depending on the teamboard configuration you can select one user by clicking his name (or selecting an empty item)

or you can select multiple users by checking boxes in front of their names

To find a user in a long list just type its name in the edit box on top.