Adding Voice-Overs

Scroll the timeline so that the playhead (white vertical line) appears where you want to add the voice-over. Then click on the mic icon to bring up the recording menu. Tap Record to begin recording a voice over. Tap Record again to end recording.

Add Video Clips with iMovie

Scroll the timeline so that the playhead (white vertical line) appears where you want to add the video clip.
Tap Video to bring up your video clips.

Tap the video clip you would like to add and then tap the curved down arrow. Want to trim the clip before you add it to the movie? Just tap it, drag the yellow trim handles to select the portion to add, and tap the curved down arrow.