Add a user account for each person on your team by navigating to Settings -> Users, and clicking "Add New User".

Next, add the users name and email, and save the user to send an account invite. The user will have to click the link in the confirmation email sent to them to activate their account.

To edit a user, click the pencil icon next to their name from the list of users. To deactivate a user, uncheck the "active" checkbox on their edit-user page.