Begin by learning some important lead sheet concepts.
Take your time on this lesson. It is not important to go through each step. In fact, I would suggest that you focus first on only trying to play the melody in the right hand along with simple R7 or R3 shells in the right hand. then move on to the next lesson. The rest of the concepts in this lesson you can learn at a later time.
I suggest you follow up My Romance by learning this song with only the Shells. Do not focus on the bassline, rootless chords, comping or improvisation just yet. Really try to master the concept of playing a melody along with shells.
To finish this path, I suggest that you take a look at the chapter on Melodic Embellishment from this lesson to learn how to embellish the melody to make it your own and add your own style to your arrangement.