Go to ‘Promoter teams’ in the menu and click on the team you want to invite people to. Click on the button ‘Add promoters’. In the field you can paste the email addresses of the people you want to invite. Below that you can also indicate which role to add them to (Admin, Editor or Promoter). Then click on ‘Send invite’. As soon as a promoter has registered, you will receive an e-mail message.
Go to this question if you want to know how to set the appearance, language and content of the invitation email.