Every one-off event has a Registration section, and the default is No Registration: people turn up or they do not. Two other options exist, and the gap between them is larger than it looks. (Recurring schedules do not take registrations. Use a one-off event for anything people sign up for.)
RSVP vs. signup
RSVP is a simple going / maybe / not going response. Use it when the only question is how many chairs.
Sign-Up Form collects a form you define. Child's name, age, t-shirt size, allergies, dietary needs, whatever the event actually requires. Use it when "how many" is not enough.
Pick the smaller one when you can. Every field you add is a person deciding whether to bother.
Guests without accounts
By default a person needs an account to register. On a Sign-Up Form event, tick Guest Registration ("Allow non-members to sign up") and anyone can sign up with just a name and email.
Worth doing for anything aimed at visitors: a Christmas service, a community meal, a fun day. A visitor who has to create a login to say they are coming mostly just does not come.
Capacity and the waitlist
Set a capacity and registrations stop at that number. On a Sign-Up Form event, tick Enable Waitlist as well and the ones after it join a queue instead of hitting a wall, so when somebody drops out you know exactly who to call, and you have a real measure of how much demand you turned away.
You can also set a Registration Deadline (Sign-Up Form events), which closes signups at a time you choose rather than when the event starts. Useful when you have to give the caterer numbers on Thursday.
Permission slips
For anything involving other people's children, tick Requires Permission Slip (Sign-Up Form events). The parent signs during registration and the signature is recorded with the registration, with a timestamp.
The legal wording is yours to set: we do not supply it and we are not the ones liable for it. Use whatever your church or your insurer already uses for paper slips. If you do not have wording, that is a conversation to have before the trip, not after.
Charging for a seat
Two different things share the word "cost". Both start by ticking This is a paid event in the Details section.
The cost line is display text. "$10/person", "Free will offering". People read it and pay you at the door. Nothing is collected.
Collect payment through EasyChurchApp actually charges the card during registration. The option only appears once your church is on a paid plan and has connected its bank account (a Stripe account) for giving. Turning it on requires two things: a price per attendee, and a fund for the money to land in (Route payments to fund). The fund is not optional, because untracked money arriving in the church account is worse than no online payment at all. If you have no funds yet, create one in Giving settings first.
The price is charged for each person on the registration, children included, so a family of five pays five times the price. The event form currently has no "per family" or "flat fee" choice. The screen says registrants pay by card during signup with no cut taken, through the same Stripe account as giving.
Checking people in
If registration is on, a Check-in setting appears: No check-in, Self check-in (a member taps a button in the app), QR code (a member scans a code at the door) or Greeter only (the front desk marks attendance by hand). Staff can also check in registrants from the event's registrations page. A greeter scanning member QR codes uses the EasyChurchApp phone app; there is no scanner on the website.
Already using something else
If your registrations run through another tool or a form you already made, set the External RSVP Link and the RSVP button on your event page points there instead. You keep the tool that works, and your website stops being the place that quietly contradicts it.