First open ig.onagilisys.com, and use the dropdownmenu at the top to navigate to the correct store, which will be the final blue subfolder under that properties name.
Once into the correct property select Items -> Screen from the left navbar.
On the next screen you will see your list of screens. Here you can add screens, edit the properties of each screen, and if you hit the button all the way on the right as seen below you will be taken to the layout editor for that screen.
Once on the edit layout screen you will be able to modify screen layout and add/remove buttons and functionality.