Remove the fill (?) vent screw, remove the top while holding tank down ,fill tank,replace top and screw on slowly,replace the fill hole screw.
I have watched many videos and read many post on this caro tank and while SS and pyrex is nice this tank has some real issues IMO.
No mater how careful I am it leaks between the end of the carto's shoulder and the tank's bottom and floods the carto lock / thread to device adapter.
IMO there should be a seal for the carto's bottom shoulder area and there should be two threaded holes and screws in the top, one for filling and the other for venting.