Login to Frontify & open your Guideline, Project, or Media Library
Click on the "Team" people icon in the PowerBar on the left-hand side
Enter the email of your team members & choose their role
Enterprise customers also have the opportunity to add users from the Usage Overview page (/usage) of Frontify, where they can be directly added to a group. If the user is not added to a group which has access to a Project, the user will only be added to the user list and it will not grant access to any of the Guidelines, Projects, or Libraries.
See here to learn more.