Note: it's cheaper to prepay for Genie+ than to add it on the day of your visit. For more information, visit https://wishful.tips/genie
Disneyland requires ALL GUESTS to not only have theme park tickets, but reserve the day when they plan to use those tickets. Disney calls them Theme Park reservations. You'll need to reserve whichever park you plan to enter first that day. They fill up far in advance, so you'll want to book them ASAP (up to 90 days in advance).
If you like, you can book your Theme Park reservations yourself after you've already bought tickets, or we can reserve them at the same time that we set up your purchase.