Hi kslac,
The cartomizers screw straight on to the top of your ecig device. You need to fill them first. I'll post a video below on that in case you haven't seen it. A cartomizer usually holds about 20 drops of e-liquid. After dropping in the e-liquid let the cartomizer sit upright for about 30 min. Here's the video, she uses different brand cartomizers but filling them is the same:
There is another fill method called the "condom" method but it is a bit messier, and having tried both methods I prefer the one in the video above myself.