Upgrading One day tickets

[Disneywithfour]

Hi
Going to islands of adventure in December. Was only going for one day but now planning 2 days - can you upgrade tickets already purchased to 2 day base tickets. If so do you need to do before 1st day entry? How/Where?
Thanks

 

[macraven]

upgrade the ticket at guest services before you leave the park the day you are there.