Hi,
First - to get a new number you need to contact the event registration team - e-mail to
PREREGQ@PCASDR.org. Best is to have a list of preferred numbers, as lots of numbers are already taken - particularly 2-digit and 3-digit numbers, and generally all Porsche 9xx model numbers. If you send a list of numbers, they can give you the first one that isn't taken.
Second - once you get your numbers, you need to put them on the car. The Zone 8 Competition Rules defined the standards for numbers (
http://zone8.pca.org/rules.php), but in general the rules are "big enough to be clearly visible and in contrasting colors". For Autocross, the minimum height is 6" - however, if you think you might like to Time Trial or participate in DE events in the future, get numbers at least 8" high - bigger is better.
For a while, you can use colored tape to make rough numbers on your car. If you are going to continue to do events, you probably want vinyl or magnetic numbers - most of us have magnetic numbers so we can quickly/easily slap them on at the event.
Feel free to ask questions. That is how we all learn.
