How to set my Nikon D3000 to take decent cheerleading pictures that will not be blurry?

I was told if I put my camera on Apiture priority and then 800 ISO It would produce great cheer leading pictures as my daughter has 2 big comps and I really would love to have nice pictures. Any advice on how to set my camera to apiture priority. I can't figure it out.
Thank you

Added (1). I just got this so I'm not trying to sound dumb. BUT I know what the big A stands for. It's the numbers I know nothing about.

The big 'A' on the mode dial.

It might have a sport setting

i have a different camera but turning the flash on always helps in action shots it seems

Aperture priority alone won't do - it'll set the shutter speed pretty much at will, according to your ISO automatic setting. You could end up with shots taken at 1/45s or so, with awful subject movement blur.

What you need is a reasonably fast shutter speed to freeze motion. Shutter priority (S mode on the top dial) will serve you better here. Use that mode, make sure that ISO auto is on, and set the shutter speed to something like 1/500s. That'll freeze most motion and the camera will keep the other operational parameters (aperture, ISO) in a way that retains a proper exposure.

Actually, I find shutter priority is one of the worst modes to use a camera in. Unless I'm panning where I need a very specific shutter speed to get the desired result, I almost exclusively use my camera in A mode.

The ISO setting is basically how sensitive your camera is to light. The higher the value, the more sensitive it is to light. This, in turn, allows for a faster shutter speed which will prevent blurry shots. However, if you set the ISO too high, your shots will also get more and more grainy. Therefore, always use the lowest ISO you can get away with that doesn't introduce blur into your shots.

Another thing you'll also need to control is in A mode is the aperture. Aperture is measured in f/stops. The smaller the f/stop, the larger the aperture. Large apertures are useful in low light because it allows more light to enter your camera, which allows for a faster shutter speed.