Can anyone explain vaping to me?

I smoked for a couple of months once but gave it up because I'm hopeless at lighting cigarettes without them snuffing out. I bought a vape once and couldn't get it to work. So I went to another supermarket and asked the young person serving me if they knew how to set it up and if I bought it, could they do it. And they did. I opened it and they showed me how to use it. But I couldn't figure out how many times you're supposed to vape on it as compared to a cigarette. With a cigarette it burns out but the vape keeps going on, so how do I know the right amount to vape?