1) Step 1 is to find a good trackday provider that will give you instruction. I enjoy Hooked On Driving events. You'll be placed in a beginner's group with a ride-along instructor to help you get the hang of it. Unfortunately, nothing can simulate a track environment. Autocross and karting are very different beasts. Be very careful not to choose the necessarily cheapest trackday organizer. I've done that before and it was a complete clusterfck with 6-7 children smashing their S2000's together. The cheapest days also attract the cheapest people.
2) Sign up for a trackday (back to back weekend dates are best).
www.hookedondriving.com
3) Buy a camping chair and a cooler. Trackdays are like fishing. Most of your time is spent relaxing and talking to other car people.
4) The car needs nothing for your first trackday. It is ready to go out of the box.