This is a difficult ask for even a dSLR shooter. A superzoom bridge camera will be further handicapped by a slow lens and a small-format (1/2.3") sensor. You may have no choice but to get motion-blurred images.
You will want to use a high ISO setting--probably 1600 or higher. Consider using post-processing software that can do noise reduction, and turning off or reducing noise-reduction in camera. Unfortunately, your camera does not shoot RAW, so make sure you have your white balance appropriately set.
The main goal here will be to get the shutter speed up high enough to stop motion blur from movement on the stage. That's going to be very hard. Blur from camera shake may also become an issue, but you can easily control that by using a tripod or monopod, rather than handholding. Movement, otoh, can be tough, because the faster the movement is, the faster the shutter speed needs to be to "freeze" the action, so get used to the idea of hands or feet being blurred, even if you can get the shutter speed up to 1/100s or so.
Focusing in low light may be an issue--it may not, depending on the amount of stage lighting you're going to get. If there is a well-lit area to focus on, aim for that. That will help. Trying to focus on darker areas of the frame are liable to cause searching/hunting from the AF system.
Also consider not zooming in as tightly as you possibly can. The longer end of the lens will have the smallest maximum aperture (f/6), and will typically require an even faster shutter speed. The wider end of the lens will let you open up the aperture a bit more (f/3.4). The problem is that for available shooting, the borderline tends to be around f/2.8.
If you really can't get the shutter speeds you need any other way, you could consider using the low light (candle-icon Scene mode) mode of the camera, but generally speaking, the smear/noise from the simulated super-high iso setting, and losing 3/4 of your sensor's resolution (i.e., taking a 4MP vs. 16MP image) may not be worth it unless you're only doing web-size images.