Below are diagrams of how to play 3 chords.
The chord below is called a C major chord.
(notice the bottom note begins on C)
C Major Chord

All 3 notes are played together with your left hand.
Finger number 5 plays C, number 3 plays E and your thumb plays G.
The chord below is called an F major chord.
(notice the bottom note begins on F)
F Major Chord

All 3 notes are played together with your left hand.
Finger number 5 plays C, number 3 plays E and your thumb plays G.
The chord below is called a G major chord.
(notice the bottom note begins on G)
G Major Chord

All 3 notes are played together with your left hand.
Finger number 5 plays C, number 3 plays E and your thumb plays G.
The way we show which chord to play in music,
is to show the chord name
ABOVE the musical staff as shown below.
