You can record video or take photos directly into your movie project. Recorded videos and photos are stored in your Photos library.
In the iMovie app on your iPhone, open a movie project.
Scroll the timeline so that the playhead (the white vertical line) appears where you want to add the new video.
Tap the Add Media button 
, tap Camera 
, then allow iMovie to access the camera and microphone (if you haven’t already).
The Camera app opens in video mode.
Tap the Record button 
to begin recording video; tap it again to stop recording.
Tip: You can tap the resolution and frame rate below the record button to change how the video is recorded.
To preview the video, tap the Play button 
; tap it again to stop.
Tap Use Video to add the video to your project, or tap Retake to discard the previous take and record new video.
Recorded videos are stored in your Photos library.
You can take photos directly into an iMovie project, for use in that project only.
In the iMovie app on your iPhone, open a movie project.
Scroll the timeline so that the playhead (the white vertical line) appears where you want to add the new photo.
Tap the Add Media button , tap Camera , then allow iMovie to access the camera (if you haven’t already).
The Camera app opens in video mode.
Tap Photo.
Note: For best results, rotate your device to landscape orientation before taking photos for use in a video project.
Tap the Shutter button 
to take a photo.
Tap Use Photo to add the photo to your project, or tap Retake to delete the existing photo and take a new one.
Note: To change camera or microphone permissions for iMovie, see Control access to hardware features and Control access to information in apps in the iPhone User Guide.