I'm aware this wasn't directed at me, but the Cap it the other section to your RDA, the piece of (generally metal) that goes over the deck. It's important that that's not being touched by your coil, as it would create an aforementioned short.
Another thing that I don't feel has been touched on, or not sufficiently. Without asking questions like this, you wouldn't learn. None of us were born vapers, so in future, don't worry about asking how/why/what happens, just do it before you physically do anything yourself.
Similarly, I believe it's important to not only be able to utilise Steam Engine, etc. But also understand the process, and why you need to know your batterie's amp limit, and the effect your build has in relation to that.
Battery Mooch (arguably the most important reference point for mech users) has long been testing batteries, his work will keep you safe, provided you're not foolish and follow the build>check>fire>check>check again>check just once more, to be certain> use methodology listed above. He's got a youtube channel discussing all things battery. While you're waiting for your 18650, pop over to youtube, start at episode one and just learn. It'll be a great help, albeit a lot to take in.