You must use the equestrian waiver for the state in which you are holding the event. If your state does not have a specific waiver, then use the General Equestrian Waiver
Large Equestrian Warning Signs (one-inch high lettering)
Any minor participating in Equestrian Activities must have their parent
or legal guardian sign for the minor on the adult Equestrian waiver
(general or State specific, whichever is used by adults at the
event/practice). Where the waiver says "Legal name", write "<parent's
name> as parent/legal guardian on behalf of <minor's name>", and then
have the parent sign.