many different method's , but mine is , engine off, fill rad at the plug use the correct size socket , brass plug will take some stick plastic one wont . when full replace and then fill at therm housing . when full , remove small pipe on left of housing , held on by a jubilee clip fill expansion tank until water leaves end of pipe , put you finger on the outlet the pipe fit's to or you will loose water . refit pipe top up tank run engine and check for leaks . be careful of the fan , open heater to hot as you start engine . you may need to get correct tank cap to ensure you don't loose pressure when engine is building up temp
this should help as i stated different people different method's , they should all add up to the same thing , cool running and heaters