I don't know the song but BIAB can have 4 chords per bar. If your song is in 4/4 time, one chord per beat the most you can do. By default, BIAB accepts 2 chords per bar. If you separate the chords by a comma, you can get 4 chords. For example: C, Am will put the C chord on beat one and Am on beat two.

By using Pushes, you can 'push' the chord earlier by either 1/8th or 1/16th. To enter a push, you type a ^ (1/8th) or ^^ (1/16th) before the chord. Try playing with those and see if you can get it to work.

There are other games you can play to get more (perceived) divisions per bar such as Edit|Expand but maybe using Pushes is your answer.

R