Go to the memorial and tap the camera icon to Add a photo. Choose to take a photo of the grave or choose an existing photo on your phone.
Photograph the grave. Rotate the photo if needed and tap the blue checkmark.
In the next step you can crop and rotate the photo, add an optional caption, and choose a photo type. When you are finished, tap Upload.
The photo will upload or be placed in a queue according to your settings, whether you are uploading using cell data or only while on WiFi.