How to Rotate or Flip Video on iPhone and iPad with iMovie
Step 1. Open iMovie on the iPhone or iPad.
Step 2. Choose the video you want to rotate from the video selection list, then tap on the ‘Share’ / action button, it looks like a box with an arrow flying out the top of it.
Step 3. Choose ‘Create Movie’.
Step 4. Place two fingers about an inch apart on the video in iMovie, and rotate them like you’re turning a dial to the direction you want to flip or rotate the video to, a little white rotate image will appear on the display.
Step 5. When the video has been rotated to the orientation you’d like to keep, tap on the “Done” button in the upper left corner.
Step 6. Now tap the Sharing button again (it’s the box with the arrow flying out of the top).
Step 7. This time choose ‘Save Video’ (optionally, you can share it on Facebook, YouTube, iCloud, etc, but we’re saving the rotated video here).
Step 8. Select the video resolution you’d like to export the movie as: 360p, 540p, 720p, or 1080p.
Step 9. When finished, iMovie will alert you the video has been saved to your Photos Library, so you can open the Photo app to look at your rotated video.