u need to open the system on 2 ends 1 to drain and 1 for air
typically u turn the system upside down and tilt and put a pan under one side then cut the line or unscrew it.
My koolance systems have drain build in the bottom - so you remove the fill cap (lets the air in) and unscrew the drain all the wate comes up.
koolance has a pump-run without the system on - you can do this for a very short while - dry running the pump will kill it.
tilt your system back and forth to get all the coolant out