Welcome to planDisney, Logan! I'm so excited that you plan to visit the Disneyland Resort soon!
I'm really glad that you are considering upgrading your
ticket to the Park Hopper option. Disneyland Park and Disney California Adventure Park are mere steps away from each other so it makes hopping back and forth a breeze. I hop between parks every day of every Disneyland Resort trip I take.
To add the Park Hopper option to your ticket, you will need to stop by a ticket booth once you arrive at the parks. I suggest you do this on the first day you arrive because adding the Park Hopper option is a flat fee per ticket; it isn't charged per day. In other words, adding this option to an adult ticket is the same price no matter if it's a one-day ticket or a five-day ticket. So you might as well take advantage of park hopping during both days of your visit!
With your newly upgraded Park Hopper ticket, you will keep your existing
theme park reservations and start at the park you have reserved for each day. Then, at 1:00 p.m. you can begin hopping back and forth between parks. I think you'll enjoy the flexibility this provides in your park touring. Of course, please keep in mind that entrance into any park is subject to capacity limitations.
I hope this information was helpful. Have a hopping good time at the Happiest Place on Earth!
-Linda