You said:
Rotate a clip
- With your project open, scroll the timeline until the clip you want to rotate is showing in the viewer.
- In the viewer, move your finger and thumb in a clockwise or counterclockwise twisting motion over the video image.When the white arrow appears, the video clip has been rotated 90 degrees. It may take a moment for the clip to appear rotated in the viewer.Repeat this motion
...I tried this, it did rotate, but no white arrow appears, and it won't stick, it flips back to sideways again. I took the video on iPhone6 in landscape view, maybe that is why it won't stick?