Admins can add users by going to:
SETTINGS → MANAGE COMPANY SETTINGS.
Users can be managed under the MANAGE USERS tab, located at the top of the page.
Adding a User:
1. Select "Add New User"
2. Fill in the user's email address:
3. Fill in the appropriate Fields and click "Save". To determine which Role they should have, check out this article for the role descriptions: User Role Descriptions