Using Cemeteries/Search Cemeteries, find the cemetery page in the Find a Grave app. Once you are on the cemetery page, tap on the list of memorials or to find only the photo requests, tap on the button that includes "# Photo Requests."
From the memorial list under the Search bar, there are Filter or Sort options. Lower in the Filter options you'll see Grave photo, No grave photo, GPS, No GPS, or Plot or No plot. Choose to filter by those options.
When browsing the list of memorials, to the side you'll see either a GPS pin or Camera icon. This means that the memorial needs GPS or a grave photo. Tap the memorial in the list to add GPS or the grave photo to the memorial.