On the Gateway webpage, go to the Configure section, and choose Security > Users, Roles from the menu on the left.
The User Sources page is displayed.
Click on the manage users link for the User Source you want to manage.
Click the Edit link for the User you want to edit, or click the blue Add User link to add a new user. (When adding a new user, you can also add their roles at the same time).
This is not showing in the Manage Users and Roles for Profile ‘blahblah’ like the document says it should or like it showed up in 7.9.9