Barely Panacan

Sensor Overlay is hard to learn from, but usefull later
Until you are good at scanning I suggest you use the Probe Scanner(Alt-P)..
BUTby default, All usefull elements of Probe Scanner are hidden They pop up under the default positon of the Selected Item window (By default: directly above the Overview). To make it easier to see and use, Undock the (Alt-P)Probe Scanner window from the Solar System Map(F9) To do this use the Open In Sperate Window icon just to the left of the 'Close X' on the far right.
->AGAIN, by default All of this is under the Selected Item window, which you need to drag out of the way to even SEE the (Alt-P)Probe Scanner window <-

Once Alt-P is sepreated from the System Map(F9) you can decide to fullscreen the map or dock it to the screen as you like. I fullscreen it. This can all be reversed in the Alt-P window> Dock in Solar System Map icon alongide the close, minimize, etc icons.
It's important to check EACH window's individual setting of Above Full Screen Views. Any fullscreen window is Top, unles you set individual windows to be above it.
So between the hidden Alt-P window and the Map you're made to scan on a default that is blocking all windows. it takes a few minutes of setup