Open the Photos app
Select the video you want to edit
Tap Edit
Tap the Music or Audio option if available
Choose a song from your library or available tracks
Adjust the music start point and volume if needed
Save the edited video
Use iMovie if the Photos app does not offer music tools
Open iMovie
Create a new Movie project
Import your video
Tap the plus button
Select Audio
Choose a song, soundtrack, or voiceover
Add the audio to the timeline
Trim or adjust the audio length
Tap Done
Export or save the video
Use the CapCut app
Open CapCut
Start a new project
Import your video
Tap Audio
Add music from sounds, your device, or imported files
Trim and adjust the audio
Export the finished video
Use the InShot app
Open InShot
Start a new video project
Import your video
Tap Music
Add a track from your device or app library
Adjust volume and timing
Save the video
Use the Instagram or TikTok editor if posting there
Upload your video
Tap the music option
Select a track
Adjust the clip length
Save or post the video