Not all pieces of music begin on the first beat of a bar. Any notes written before the first full bar are called lead-in notes (or pick-up notes). When lead-in notes occur, the final bar of the piece is also incomplete. The lead-in notes and the notes in the last bar add up to one full bar.
This song is an early Jazz standard made popular by brass bands in New Orleans. It contains three lead-in notes. Hold each whole note for its full value and take a breath on the following quarter rest.