Hi Asoon88,
Thanks for your reply. My issue is if I don't dismantle the rocker buttons, the two side (left and right) screw holes are concealed by them and there is no way for me to secure the switch to the wall mounting box. Unless there is a way I can access to the two side screw holes without dismantling the rocker buttons.
Really hope that Legrand can provide a more elaborate installation guide, but the small piece of paper comes with the switch only shows a simple diagram that indicates both the faceplate and rocker buttons need to be dismantled first before securing the switch to the wall mount box using the side screw holes.
Thanks !