iOS 9 Photos in on-phone album in random order: how to rearrange or sort?
Sorting Manually In an album that you made (not a smart album like Time Lapses or Selfies), to move a photo around: head into that album, press Select in the top-right, hold down on the photo you'd like to move, and drag it to the place you'd like to move it to.

Sorting by date or name In the Photos app on Mac, go into an album, press "View" in the menubar, hover over Sort, and choose to either sort by date or by name. 

Hope this helps!