Apple wallet

Airline Tickets (reservations) are not added to Apple Wallet.

Airline Boarding Passes are added to Apple Wallet as part of the check-in process; generally from the airline's app or web site.

See more info here:

Add, use, and share boarding passes, tickets, and other passes in Apple Wallet - Apple Support

Gotcha ... bad assumption on my part ... sorry.

Then you'll need to contact the theme park and/or the ticket seller.

If they provide the ability to add their tickets (passes) into Apple wallet, it's almost certainly implemented either thru their iPhone app or possibly thru their web site.