https://www.acer.com/ac/en/ID/content/support-product/4549;-;

https://wiki.debian.org/InstallingDebianOn/Acer/Iconia_Tab_w500/squeeze

F2 gets to BIOS, F12 gets boot prompt.

Booted from debian live USB to test, then installed from live USB.

During boot, volume acts as up/down (for grub, bios, etc) and windows button acts as select. power down the system completely

disable secure boot

Connect an external USB DVD drive using the micro USB to female USB adapter.
 Enter the bios by pressing F2
Tap on Security and set a Supervisor password.
Select the Boot page and then Disable Secure Boot.
Under Boot priority order, use the arrow buttons to set the USB CDROM to the top of the boot priority order.