((1)) open lid
LIFT OFF THE TOP LID TO REVEAL THE battery compartment
((2)) insert batteries
insert 4x fresh AAA batteries.  
((3)) switch on
slide the orange power-switch on the top right to power on the unit.
((4)) on
when switched on, the led screen will light up immediately.
usb
you can also power the unit via a standard usb-c cable (5V / min 1A). we recommend using a quality "USB-IF" compliant charger.
update
keep your K.O. II up-to-date with the latest firmware by going to the update utility.