Procedure after replacing rear air suspension strut Q7

[sluggs1]

Looking for some advice, i am replacing both my air rear struts and wondering what is the procedure when finished, obviously there is no air in the unit, will be doing one at a time on a jack, so after fitting back on the car will be on the high height mode in jack mode, do you start the car and let the compressor inflate the strut as usual and then let it down or do you let it down on the ground and let it fill when down on the ground??, checked all the Arnott videos and they show how to do everything but this? any ideas out there??