you really should get a tripod. There are some small compact ones you can buy. It doesn't have to be a hulking big one, but you really need one to take great fireworks picture.
On your camera, turn the dial to landscape mode, turn off your flash, set the camera on a tripod and shoot away. Best bet is to shoot using the self timer to really minimize shaking. Use the highest resolution you can get, don't bother zooming in, you can always crop later.
If you don't want to spring for a tripod, then stake out a spot where you can put the camera on a trashcan/low wall, etc - something where your camera can sit and not move.
Good luck.