Learn to play this melody by Bach with your right hand alone, then you can add the chords as they are written. You will use the I, IV, and V7 chords in G Major. You will also use and e minor and an a minor chord.
Use correct fingering (the numbers between the treble and bass staves) and you will have a smooth melody.
Instead of playing the chords that are written in the bass clef, you can add the automatic chords by reading the letters above the treble staff. The melody starts on the count of 2, and you start the chords at the beginning of next measure when you play the B in the melody.
The rhythm you add will be a waltz since the song is in 3/4 time. Begin ver-r-ry slowly with a metronome speed of 60.
When you can play it well at that speed, then try it faster.