At the left side you have the navigation menu with your project and your modules.
When you double-click on ‘security’ at the project level (It should be the highest level, and it has the cube as a symbol), there will be a pop-up with the User role tab.
If you don’t see the navigation menu at the left side, try to reset your layout (topbar => View => Reset layout)
Hope this helps!
Thanks Daan, that solves the question. Maybe changing the snapshot to show the complete context, like that, would help newcomers like me understand more rapidly: