You very much need to read the manual and get a basic understanding of the operation of the camera. It will tell you how to understand and use the built in light meter. Once you can use it you can begin to use one of the control modes. AV, TV, Manual and begin to make adjustments.
Once you understand the light meter, and can use the controls to change the Aperture value, shutter speed and ISO you can find the settings necessary. When you are in the venue start with setting the Aperture as wide as possible. Check the meter and see if you are underexposing or overexposing. Then dial your ISO either up or down until you have the shutter speed that is fast enough with the meter showing a proper exposure. 1/320th would be good, 1/500th would be ideal. Don't try and overdo it. Boxers aren't that fast. No need for 1/4000.
Let me also toss out a couple of challenges you are going to likely face. If you looked at my gear, any Canon shooter can tell you this, my glass is all top notch. My bodies vary from mid range to top range in the 1D MIII.
The kit lens for sports is slow. I have never shot Sony so I can't speak of the quality of the shots wide open. All lenses tend to be a bit soft wide open. With top quality glass you can usually get a very usable quality shot.
Also the slower glass is going to cause you to use higher ISO's than fast glass would. Higher ISO's mean more noise in the shots. Again, not having used Sony in the past I can't speak to their high ISO quality.
You are just going to have to learn your gear and work from there. One little tip I will give you. Every lens needs a hood. Protects the lens from lens flair, bumps and such. It also gives a sports shooter a place to store valuable information on venues they shoot. My lens hoods are covered on the outside with little notes stuck on them on the settings for different venues. AV, ISO, Shutter speeds etc. This is for both indoor venues and outdoor stadiums I shoot under the lights. It makes it a quick and easy way to dial in your settings when you revisit that venue.
Good luck and practice, practice, practice.