Hello Jennifer, and welcome to planDisney!
You will not believe this, but I am in the process of adding a night before my upcoming
Walt Disney World Resort stay, so this question has come at the right time.
To add the day before or after your planned stay, log into your
My Disney Experience account (via the website) and select “My Plans.” You will find your reservation, and next to that stay, you should see the option to “Change Reservation,” and from there, you should be able to see the available modifications. Select the “Change” option and proceed through the process. If you are not given the option to make the change via the website, it will be a good idea to call (407)939-1936 and get the assistance of a cast member. Please note that the ability to make any changes will be based on availability.
We will be here if you need us; please let us know how we can help.
Have a magical time!
Raquel