you want to bleed the cooling system.
top up at tank
leave filler cap off
start engine
put driver and passenger heating to highest temperature , indicated at 32 c with dual zone climate control .this fully opens heater valves , some folks just hit the max button .

rev engine to around 2500 rpm to circulate coolant , only at this rpm will you see coolant flowing across the tank fill hole .

a few minutes of this should have the system bled .

any more questions , purchase and refer to the bentley manual or take car to a mechanic .