Gather Images to Drag and Drop — iOS11
Drag and drop allows photos to be moved from the Camera Roll to any of your own albums (in the My Albums section) or between your own albums.
Once you’ve found the first photo you want to move, long-press (or press and hold) on it to highlight it.
Drag the highlighted icon slightly away from the main thumbnail underneath it (Image 1). Once you’ve highlighted one image and dragged it slightly away from its main thumbnail image, tap on the next image you want to select while continuing to hold the first (Image 2). Tap a third image and it too will be added to your selection.