How to add photos to an existing Facebook Page Album via my iPhone?

I have a Facebook Page, which I have 3 separate photo albums. I do not wish to upload photos onto the wall and "mobile uploads"… I want to sort my photos and add them to either of those 3 albums as I please.

When I go into one the albums, there should be an option to add a photo, but there isn't… All I can do is view the photos already uploaded.

Go and share it through photos.