From N2 - a number of people ride with them on the forum: https://www.n2td.org/faq/
Different orgs have different rules, but overall they are fairly similar. Really it's just about showing up, accepting you're gonna be slower than a lot of the people there, and focusing on learning and having fun. Also remember to bring shade, something to sit on, some form of hydration maybe some bananas and some sodium to help stay cramp resistant and not get dehydrated. I can down 2 bottles of water after every session all day long and never have to pee, it creeps up on you fast.
A video I found that might be helpful? I didn't watch all of it: