Take both plastic tops off with a little tool.
Put about 22 drops of liquid in one of the plastic condoms.
Very SLOWLY push the cartomizer, battery side down, in the liquid.
Go slow, when you see the liquid come up, stop, and then try again.
When the plastic condom is empty, but the white fill at the top still looks dry, add a drop here or there on top.
Put both plastic tops back on, and you're ready to go.
When refilling them, do the same, but only put 10 drops of liquid in the plastic condom.
My experience is the more you fill them, the less liquid it will take.
Don't let them get too dry, because the fill will burn.