So, let’s add our chords to the melody. We are giving the first chord as E5. We sing the melody, while trying out the chords against the melodic tone.
The tones of the chords are included, as well as the tone names of the melody. We can use some logic to create possibilities. If the melodic tone is in the chord, the chord may work. Or, it may not. Our ear tells us if it is the one.
If the melodic tone is E, and E is in the E or A chord, we can try both of those. Which one? Our ear will tell us.
Experiment your way into your answer, then look at ours.
Hint: the chord doesn’t have to change on every new melodic tone.