I have a Pink Riva 510 and have cartomizers for it. So I figured out how to put it together (thanks to youtube) and what I do is take the part your mouth goes on(the white rubber part) and take it off and drop the liquid inside. My worry is I'm not quite sure how to tell if it's full or if I put too much or not enough. What a dumb question... I know but I just don't want to mess it up.