In order to let your customers add photos from their Facebook account, you need to create an app in the Facebook developers center. After that you need to start an App Review and asking for the permission user_photos in a submission to Facebook. For this submission you also have to capture a screencast of the Facebook login process in the product designer. So the Facebook developer team sees where the Facebook login can be found and what you are doing with the photos.
Here is an example for the screencast:
The reviewing process can take some time, it depends on Facebook. In some cases Facebook is asking for some extra information, which can not be exactly specified by us. In this case you have to discuss it with the Facebook developer team.