Most of the sheet music you buy will be arranged for piano. Piano music is written using two or three staves, with the chord symbols written above the top staff, as shown in the example. It may also contain unfamiliar symbols and terms.
At this stage you need only look at the top staff, which contains the melody line (tune), the lyrics and the chords. You will however, need to have a knowledge of keys and key signatures which are discussed in detail in Progressive Theory by Peter Gelling.