The mainboard is connected to the top of the case by four Torx 5 screws and held in place by two, small plastic guide pins in the top and bottom right corner (see arrows)

Use a Torx 5 bit and remove all of the screws

Ensure that you have removed the two ribbon cables connecting the screen and LEDs, before you remove the mainboard

After removing the mainboard, pull out the two white rubber bars for the LED lights.