Hey there Chelsey,
Welcome to planDisney and thanks so much for your question! It looks like you're headed to the parks soon - how exciting!
The good news is that the vast number of Disneyland Resort park tickets can be upgraded in various ways to equal or greater value versions. It all depends on what specific upgrade you're looking to make.
If you have a 1-day park ticket for a lower tier but your plans change and you'd instead like to visit on a higher tier date, or you'd like to add on a day to your tickets, or you'd like to add the Park Hopper option to your ticket, then you'll want to
call a Cast Member at the Tickets line for additional assistance and to walk through your options.
If instead you're referring to
upgrading your park ticket to a Magic Key then you check that directly through the Disneyland app! Just pull up your ticket in the app and select the “Upgrade to a Magic Key Pass” button. Note that for 1-day tickets you'll need to upgrade by midnight on the day of your visit to the Disneyland Resort, and for multi-day tickets you'll need to upgrade by midnight on or before the last valid day of your ticket.
Thanks again for your question, Chelsey! I hope you have fun making new magical memories at the Happiest Place on Earth.
Have a Magical Day,
Greg