Bike handlebar installation help?

I tried replacing my handlebars, but realized once I tried putting the new one on I had no clue what I was doing. It's a threaded quill stem with a wedge, and when I put it in it doesn't hook onto anything, it just spins. There is a screw at the very bottom of the tube you put the stem in, but the wedge doesn't reach that far. Anyone shed some light on this please?