Yes, it may seem simple enough, all you have to remember to do is " take the lens cap off".  But Wait, maybe you don't want it to be so simple. Imagine what you can achieve if you're willing to shake things up a bit.

Try this:

With your camera on a tripod and the shutter set to B for bulb,  you can easily obtain multiple exposures of fireworks. 

First, hit the shutter.  The shutter will open...but with a lens cap on, no light will enter the camera.

Then, as you hear the dull thud of the launcher and see the streaking fuse heading to the heights, you can pretty well judge when a big burst will happen.

So, just before that explosion of shape and color, and with that shutter still open (on bulb), remove the lens cap and capture just the climax of the  pyrotechnic.  Then, cover the lens and wait for the next launch, repeating the process until the entire field of the photo is filled.  Obviously, some experimentation will be required, but you'll have a blast with this one, cobbling together an unending variety of color, motion and dazling sparkles.

And don't forget that you have the option to point the camera at different areas of the sky.