Michael is right about concert photography. A superzoom like your FZ18 is a good way to get started. But pro concert photographers are using lenses that cost more than your camera in order to squeeze as much light as they can in the poor conditions. But that doesn't mean you shouldn't try or you can't get good photos. I've seen very good concert photos from superzooms like you have. Try setting the ISO to 800 or 1600 and put the camera in either shutter priority mode. The higher ISO will increase the light sensitivity and shutter priority will allow you to make sure your shutter speed is fast enough to freeze action and stop camera shake. The Mega O.I.S. image stabilization helps with camera shake. But in the kind of conditions you're shooting in, you need all the help you can get. So experiment with shutter speeds to see what you can get away with. Anything slower than 1/15th second you're very likely to get blur because your subject is moving. And the more zoom you use, the more likely you are to have a problem with camera shake. This would be really bad if you were shooting film. But since you're using a digital camera you can check your images as you shoot and tune them up as needed. That's one of the biggest benefits of a digital camera.

Hope that helps. Your camera should be able to do pretty well. And practice and experimentation will make a huge difference. It also helps to post problem photos here and ask questions. If you don't understand why something didn't work, posting a sample for us to look at is a good idea. If you tell us the settings you used we can probably give you some suggestions for improving during your next concert :-)