Hello, Simon and let me offer you warm greetings from planDisney!
Simon, I'm so glad you stopped by with this question and hope I can help as you're planning out your day at the
Disneyland Resort. To upgrade your current ticket, you'll need to visit one of the
Guest Relations (or ticket booth) locations on the day of your visit. You can easily view a list and map of all the Guest Relations stations
HERE.
Now, prior to visiting, please make sure that you've secured your
complimentary theme park reservation as all guests are required to make a reservation in addition to your valid park ticket to gain entry. Once you have
upgraded your ticket, you will be able "hop" to the other park (subject to capacity limitations) at 1:00 PM.
I hope this information is useful as you're looking forward to a return to the Magic. Whether you begin your day at
Disney California Adventure Park or
Disneyland Park, I hope your first step through the gates has you smiling from ear to EAR.
Please come on back to planDisney with any additional questions you might have.
Lauren