At the moment the manager's email seems to be stored as a user custom field in the user's profile. By default facetoface looks for a custom field with a shortname of 'managersemail'.
So to set up for a user, first check that you have a 'managersemail' custom field:
1. As administrator, click Site Admin > Users > Accounts > User Profile Fields
2. If there is a field called 'managersemail' you're all set
3. If there isn't create a new profile field with type 'text input'.
4. Set the shortname to 'managersemail'.
Once the field exists, you can edit it via the user's edit profile page.