When you first boot up you will see suggestions along the bottom of the screen for a couple of keys to press.
One is for Set up and the other is for the one off boot options.
The "Set up" key will get you into the BIOS and for an Acer could either be F1, F2 (usually), or a combo of pressing CTRL+ALT+ESC together.
Tapping whichever of these as you switch on will get you into the BIOS.