When it comes to chord charts like these, generally, you know when to change chord based on the lyrics.

For example, the song starts with the C chord as the singer begins with "What can wash..."

But when the singer gets to the end of the word "wash," you must change chords to A minor, and so on.

Chord charts like these are easier if you listen to the song, and try and play a long that way.

Hope that helps!