Hello, Courtney! Welcome to planDisney!
If you purchased tickets before
Disney Genie+ launched at the Disneyland Resort, then the only way to add it on to your ticket is through the
Disneyland app after you have entered the parks. Once your ticket is scanned, you will see the option in the app to purchase Disney Genie+ for $20 per day, per ticket. If you have multi-day tickets, you will purchase Disney Genie+ on each individual day.
Don't forget that downloads of your Disney PhotoPass photos taken on a day that you use Disney Genie+ are included. So be sure to stop by the various Disney PhotoPass Photographers stationed around both parks. Show the photographers your PhotoPass QR code in the Disneyland app when you have your photos taken and they will be automatically linked to your account.
I hope this helps. Have a great time at the Happiest Place on Earth!
-Linda