Determine the key that the piece is in. The key will determine which notes to pick. Check the resource section at the end of this article for a tutorial on how to determine the key of a piece.
Create an interval of a third above the note written in the score. This will be the first pitch to add to the initial note. Make sure to keep the note within the key in order to create a chord that fits.
Create an interval of a fifth above the note written in the score. This will be the top of the chord. When played together, these three notes make up a chord. If your bottom note was C and the piece is in C Major, the resulting chord would be C E G.
Follow step 1 from the first section. The note that is being built upon is now the third of the chord, but it will remain in the bass to create a first inversion triad.
Follow step 2 from the first section. This note will be the fifth of the chord, but it will remain as the second note in the chord from the bass.
Add a sixth above the bass note. This will be the root of the chord, but it will be put in the position of the third note in the chord from the bass. By following this process, a first inversion triad is created.
Follow step 1 from the first section. The note that is being built upon is now the fifth of the chord, but it will remain in the bass to create a second inversion triad.
Add a fourth above the bass note. This will remain as the second chord member within the chord, but it will function as the root of the chord in second inversion.
Add a sixth above the bass note. This will be the root of the chord, but it will be put in the position of the third note in the chord from the bass. By following this process, a second inversion triad is created.