From OpenSCADAWiki
Booting
To boot from the live disk the computer should be rebooted and then you should press the key to enter the BIOS boot menu at the very start of the boot and choose there our disk (Fig.3.1). The key to enter the boot menu may be different on the different computers and may be one of the following: "F8", "F9", "F10", "F11" or "F12".