what most of us would do - at least I think so - would be to enter the chords and then choose a BIAB style that fitted and then use that as a backing track with any minor tweaks we wanted. I don't think any of us would enter the sheet music note for note. Sometimes songs have recognisable riffs - and they can be entered manually to match the recording. But entering the notes for a complete song is a major task and if you want to do it its probably best to start with a blank sheet as editing the Real Tracks will mean starting from scratch anyway as its unlikely they will be close to the sheet music. I'm not even sure that all RTs are editable. (Others may correct me.)

However, if you want note for note then other programs will scan in the music and then you can create a midi file. BIAB isn't really designed for note for note performance of sheet music.
Other forumites may be able to suggest another program that would be better for you. And don't forget, I think the sheet music is copyright.