Lip-sync takes in, finished edit out. Every take syncs itself to the song and cuts land on the beat.
Film each take with the song playing out loud. The app listens to each clip and finds where it sits in the song, so takes can start anywhere. More takes, more angles, better edit.
Paste your lyrics, one line per caption. Then hit Tap to sync and tap (or press space) right as each line starts. Lowercase, squeezed, a little blurry.