See Prusa i3 Plus kit assembly - 6. LCD for a complete visual assembly guide.
You'll need to extend the ribbon cables before installing the LCD at the front of the printer. Right now, the cables I'm using are 60cm long each, the panel is still functionnal.
Slide the brackets on each side of the printed circuit board (PCB) on the rear side, open holes faceup. Insert the PCB into the cover while aligning the brackets with the slots. The inside of the slots and the surfaces of the brackets must to be clean.
The brackets then snaps on the threaded rods at the front of the Y carriage.