Over the EKP IV picture left, move your cursor. There are 16 sensitive areas. When your cursor meets such a sensitive area, it changes shape.

Then click to display the relative explanations.

As an example, if you click on the "EKP IV" logo bottom-right, you will see the physical sizes for the EKP IV. Same applies for keys, or parts of the screen areas.

The ? bottom-left leads you to basic questions such as "How easy is it to create a flight plan, ?". You then use the menu that opens below the picture.