I think there's a couple ways to get to the same place to do what you want.
Try:
Pressing the "Inst Group" button in the lower right side of the screen (Currently hidden under the Artificial Horizon instrument in your image).
Then in the bottom, left side of the box that appears, click on "Customize".
Now press "Add Instrument".
Scroll down to the line that says "EFIS Toggle" and click on that.
Then Click on "Add"
You will now see the "Show EFIS" Button outlined in red in the center of your screen. Drag the button to where ever you want it located on your screen, then;
Press "Save" (or "Add Instrument" if there are more instruments you want to add to your screen)
iFly will now give you a choice to save it as the [Same name as the] current layout, or give it a new name such as "Basic with EFIS".
Click the button of your choice, and you will either be done, or need to supply your new name, to then "Save"