I'm by no means the most experienced participant myself but its really as easy as signing up for the race and showing up to get into your first event. The only expense is the entry fee for each race. There's no special membership required and you can jump in at any time of series schedule. Others may chime in with better direction than me but here's my suggestions on how to get started:
1) Got to Live Laps (
https://www.livelaps.com/promoter?12791) to register for the TSCEC races. You'll need to set up a Live Laps account (which is just basic contact info, user name and password), then register for the particular upcoming event you want to enter. When registering you can choose which class you want to compete in and there's even a "comment to promoter" section where you can request specific row # or that you and your friends/family are on the same row together.
2) Find the race flyer either on the TSCEC Site or the Sponsoring Club/Host website or Facebook page. Here's where you'll find the critical dates, times and most critically the "Where". The great fliers have actual address', GPS coordinates or Google Maps key words. The bad fliers have directions from towns other than the one you'll be coming from.
3) On race day (if your not camping at the race site) get there early and find the registration area. If you pre-registered on Live Laps they'll have your registration info and number plate. You'll need a transponder and you get that at registration. If you didn't pre-register you can do so the day of, but its unlikely you'll get to be on same row as friends and there's usually a line which can make the first time even more nerve wracking, so pre-register if possible. The folks at registration are always SUPER FREINDLY and more than happy to answer questions and help.
4) Be sure to make the riders meeting. Usually starts 1hr before race time by the registration area. Here's where you'll get instructions on where to go, heads up on course markers, etc. and a reminder to let faster riders by.
5) Your Race # is also your Row #. Lots of riders will be milling around the starting area. Look for the other guys in your row and kind of "fall in" with the procession to the starting line.
6) Once in line with your row, you've made it. Now your going racing!
Things to bring:
1: Gas can. Make a "Flag" with duct tape and put your row # on the flag with a sharpie marker. This will help you find your can at the gas stop. There'll be "gas can" trailer that will take the cans to the gas stop and set them up according to the row # so they're easy to find.
2: Hydration pack. Put some granola bars/clif bars, etc. in it so you can eat something between sections. Some guys will attach a feed bag to their gas can too. Your going to burn a lot of calories.
3: Tools. Same ones you take with you when you go ride in case you need to work on your bike pre race or something. Not a bad idea to take a mini set of the bare basics in your pack in case you have a problem on the course.
4: Waterproof/Windproof top layer. Some of the races are in cold months and you'll be warm in no time once the race starts, but sometimes its good to have something that'll keep you warm till start time and is easily stowed away once your out on the course.
5: Positive Attitude. Aint gonna BS you: These enduro's aren't exactly cake walks, but they're doable and a ton of fun. Your likely going have a "get off" or two. Your going to get passed by faster riders. Your probably going to be physically challenged. Stay positive during all of it and you'll be hooked and want to come back for more.