This can be done with those simple steps:
Go to the Users tab in your Project settings
In the "Invite users" section:
Enter an email address
Select a team
Click on Invite
Your pending invitations are listed below the user list
To manage a user's teams, go to his details page.
From there, you can:
(1) Add him to a new team
(2) Change a team he belongs to
(3) Remove him from a team
Don't forget to save afterwards
To remove a user, go to a user's details page (1) from the Users tab:
You can then remove a user from the Danger zone by clicking on "Remove user" (2). Confirm by typing "CONFIRM REMOVE" (3).
To add a profile picture next to your name at the top-right of your interface, you need to create a Gravatar account.
Create an account and refresh your Forest Admin interface. Your picture should appear.
User tags are useful for the scopes feature: they allow you to organize your users into groups and control the data they are able to see.
On the each user's details page, you can add a tag (1), edit an existing tag (2) or remove a tag (3).