Although it’s been possible to create photo albums in the iOS Photos app for a while now, the feature becomes even more useful with iCloud Photo Library and the impending final release of Apple’s Photos for Mac app. Now all of your photo albums from iPhoto or Aperture can be synced via iCloud Photo Library onto your iPhone, eliminating the need for managing this data in two places. One thing you may notice, however, is that new photos added to your iOS Photo Albums are not sorted in any particular order — they’re simply added to the end of what’s already there.
The good news, however, is that you can actually reorder these photos manually. Apple doesn’t make this obvious at all, but if you tap on the “Select” button in the top right corner, you can then simply tap-and-hold on any one of your image thumbnails and then drag that image and release your finger to drop it anywhere else in the current album. Unfortunately, this only works in user-created Photo Albums; you won’t be able to reorder photos in any of the built-in albums such as “Favorites” nor can you reorder photos in iCloud Photo Sharing albums.