My fireworks pictures were nowhere near as good
Keep practising.
?100 on fireworks per day and you will be an expert within a week
Joking aside, just made sure you use a tripod. You may need to experiment a little with shutter speeds. I have taken some at 4 seconds but 3.2 is probably my average. Blacklac's advice on 0.5 to 2 seconds is good too and his photos are excellent. Manually set the ISO to 100 and try not to touch the camera at all after you have touched the shutter button. Also, try to gauge where the wind is coming from when photographing fireworks. You don't want your shots ruined by smoke.
I've posted a few firework photos before but I've just reframed these ones recently as I've been on a bit of a reframing mission. Bear in mind that sometimes reframing can give you the chance to save an image that doesn't seem good at first. Kinda handy with some firework shots as they do tend to explode at different parts of the sky so you may be able to improve a shot when you sit down and review them afterwards.