If you want to add additional users to your Provider or Advertiser account you can easily do this in the settings of your account, which you can access via the side bar navigation:
When creating a new user the following information is mandatory:
Email
First name
Last name
Contact information can be added optionally:
Phone number
Skype contact
Once the new user has been saved an invitation email will be send to the email address so the new user can set up the password, and use the account.