This side panel is way easier to just slide out with the mainboard - so it's best to just unscrew it now so it doesn't hamper later efforts!

Remove the 2 screws from near the IEC connector - 2x10mm (or may be 2x8mm - I got these mixed up first time I pulled it apart so I'm not sure! either fits)

Remove 1 screw from near the VGA port - 3x6mm Silver Coloured