Don't know how to recover photos to telephone device after backup

I have an iPhone 6 Plus which I need to return for replacement. I went into iTunes (for the first time) from a Mac Air. I performed backup successfully but now my photos are showing on the mac Air and are no longer on my phone. Now I'm even questioning whether I performed the back up correctly! Can anyone please help me retrieve my photos in lain english, as I am admittedly NOT a technically inclined!! Thank you so much.