Como Restablecer Un Ordenador

Is there a way to download photos I have stored in a Dropbox folder to my iPhone Photo Stream using the Dropbox iOS app? There should be a way to do this but I can't figure it out. I know there's a "Make Available Offline" feature but that doesn't appear to be it. (I can't figure out what that's for either but that's another question). I just want to be able to download photos to my iPhone Photos.