Open your scale book to the B-flat-major scale and study the key signature. The key signature has two flats, one for B and one for E. In the treble clef, B-flat appears on the middle line of the five-line staff. E-flat appears on the top space directly below the top line. In the bass clef, B-flat appears on the second line from the bottom, and E-flat on the second space from the top. Circle the flats in the key signature and the notes on the flatted spaces or lines in the B-flat scale.
Play the B-flat scale, lowering the flatted notes one-half step below the natural note. In this scale, the flatted notes correspond to the black keys just below each B or E on the keyboard. The notes of the B-flat scale are B-flat, C, D, E-flat, F, G, A and B-flat. Practice the scale up and down several times. Check your pitch with a keyboard if you play another instrument.
Take out beginner's sheet music in the key of B-flat. Play the notes, making sure to play B-flat instead of B and E-flat instead of E every time. Go slowly at first. Once you have mastered the piece, practice the music faster.
Watch out for natural signs before any note written on B or E. A natural sign undoes the flat for the measure in which it appears. Play B natural or E natural instead. At the next bar line, the key signature goes back into effect, and B and E become B-flat and E-flat again.
Observe other flats and sharps added to the song as well. If the music has a flat in front of another note, lower that note one-half step for the current measure. If the music has a sharp in front of a note, raise that note one-half step during the current measure. These exceptions lie outside the key, but they do sometimes occur.
Continue your practice reading and playing music in the key of B-flat. For each practice session, start with the B-flat scale to reinforce the habit of playing B-flat and E-flat. Then practice your older pieces in B-flat and read new pieces in B-flat so you become skilled at reading this new key.