First login to ig.onagilisys.com. From the dropdown menu at the top, make sure you are in the final subfolder in blue for each property, for example in the below image, I am trying to manage users for WE Aspen Retail.
Once in the view for the property, choose Employees -> employee from the left side bar.
Once here you can add employees by pressing the +Add button in the top right, or review user ID's which is the number you use to login to the POS terminals for this property.