If you haven't been to any sprint/track days, go along to afew as a spectator first and see what it's all about. Have a chat to a few competitors - most are only too willing to offer helpful hints for your first time out.
Once you think you've got it sussed, just dive in, but if you can do your first event with a few friends it makes it much more enjoyable - swapping stories is what it's all about.
You won't be driving at ten tenths on your first time out, nor your second, no matter how much horsepower you have. You will get a feeling of what you can and can't do after every lap and only improve as you go. Your lap times will drop at a very rapid rate to begin with as you become more confident, then you can start experimenting with different lines, braking points and car set up to drop them further.
Just go for you it, you will learn a lot and have a ball.