The chords in The Real Book (or any fake book) only tell you the general outline of the harmony. Playing them as given will not include the melody (except by occasional coincidence).
To realize the music means to arrange the notes of the chords and melody so that they can be played together. The chord voicings you choose -- that is, the specific way you play the notes -- will facilitate playing the chords and melody together.
To get started, a good general rule is to play the chord's letter name as the lowest note, and the melody as the highest. Other chord notes can be fit in between in whatever arrangement is convenient. For example, for a C7 chord with an E in the melody, you would make C the lowest pitch, the E the highest pitch, and fit the G and Bb in where you can.
Keep in mind that sometimes the melody will include notes that are not part of the chord. The above rule can still apply — keep the melody on top.