No u can't practice, or at least in places I know of. Auto-x is a track made up of cones so each event will have a different track. Here is what u need to do.

Saturday night: Clean ur car out of everything thats loose including your floormats. Also its good to get more air at this point. Hmm I use low profiles at 42/40 psi. Try putting in ~40psi or maybe a bit less. The reason is, when u turn really sharp u don't want to run along on the sidewall of the tire.

Sunday: Wake up early get breakfsat all that good stuff. U will need to sign up as soon as u arrive. The quicker the better. Then u go to get ur car teched. An official will inspect your car for any loose objects. That means inside, trunk, and under the hood. So no subwoofers LOL.
After tech u need to walk the course as many times as you can. Everyone will reccomend u to walk with a pro but I like to walk alone. Pros will tell u how to take corners and give u a LOT of info u will forget the instance u hit the gas. Just focus on remembering the course.
When ur time is up either go to your work assignmemnt or into ur car. Oh forgot to mention everyone has to work. Its cool if u get to work first since u can stay out on the course and watch the other cars go by, further memorizing the layout.
Not much to say about the actual racing part. Just don't hit any cones and make sure u know how to tackle the slaloms. Some are optional and others u have to take a certain way. Just have fun ur first couplke of times. After that u can start looking for tips on how to improve and all that good stuff.


Hope this helps