How to do Triads

This is what I do

First of all, look at the key of the piece. Let's just do a random one and say D Major for an example. Then write out your chords - you never write out chord III, it's not on the JC course.

I - D F(sharp) A
II - Em G B
IV - G B D
V - A C(sharp)
VI - Bm D F(sharp)

To clarify, chords II and VI are always minor! If you do not say Minor, that's incorrect then what you write down. Also make sure you write in your sharps and flats.

Then look at the notes at X / Y or whatever it calls it on the paper, name them and then look at your chords. See which chord fits the three notes. By the way, the first note of each chord tells the name of the chord. See the D Major chords for example:

I - D F(sharp) A - D Major chord
II - Em G B - E Minor chord
IV - G B D - G Major chord
V - A C(sharp) E - A Major chord
VI - Bm D F(sharp) - B Minor chord

A triad / chord is the 1st, 3rd and 5th notes of any scale.