Read the chord

Three noteheads stacked in a column sound together. In root position they sit on three positions in a row — all lines, or all spaces — and the lowest one is the root.

So read the bottom note for the root, then work out the quality the way you already do: 4 semitones then 3 is major, 3 then 4 is minor.

Name the root first, then pick the chord.

a stack of three, all lines or all spaces: a triad in root position

D, F, A on three spaces in a row: D minor.

Practise this in the trainer — it opens with this lesson the first time the concept comes up.