From FYEO, on the Your Gallery page
ADDING PHOTOS TO YOUR GALLERY
When you submit a new post (or edit it), all the images in that post are automatically checked for EXIF and if camera and lens are found (matching our gear database) you are presented with a prominent "ADD TO GALLERY" command button placed on each applicable image. Please note: The EXIF check takes a few seconds per image, if you do not want to wait, come back later to see the results.
If "ADD TO GALLERY" command button is not there over the photo: click "EDIT METADATA" text above the photo, then follow instructions given by the metadata editor that opens. Basically, just make sure that camera and lens are picked, then submit the data. We have a rule for minimal metadata (camera and lens) for each image in gallery, the metadata editor will explain and help you to make it so if the EXIF is not automatically found or matched to our gear database.
IN SHORT: When you photo has a camera and a lens in EXIF info, you have a permission to add it to your gallery. Metadata editor on top of each photo lets you add the EXIF if our automatic system does not get it.