This can be done with those simple steps:
Go in your project settings
Select the desired Team
Fill the field ‘Invite people’
Click on Invite
You can manage access to the different teams by checking the box next to your teammates' names.
If the box is checked, it means that he/she will have access to this team.
To remove a user, go to the Users tab. From the list of users, find the user you wish to remove and click on the trashcan icon.
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.