You can invite team members under the Account ► Manage users in the Setup menu. You'll see a list of users and their roles. Click a user name to to edit details or to change the password.
Click Invite user to invite new user. Enter email address to send an invitation email.
Invited user will receive an invitation email.
Before user has taken an action to complete the registration, a status 'pending' is shown in the users list for that user.
You can resend the invitation by clicking Re-send invitation in the user details at Account ► Manage users ► [click user name]