Each chord will have a first, third and fifth note with the bass note duplicating the root note in the chord.
In other words, the soprano, alto, and tenor will form a triad which may or may not be inverted.
You don�t want to have missing thirds and fifths.
Write the melody which is the soprano. Don�t have a lot of large intervals. One step at a time is best most of the time.
Write the alto.
These two notes may not sound well together without the tenor.
Soprano and alto only sound well together when they are thirds and sixths.
You may need to go back to the alto and change it or the tenor after the tenor is written.
Write the tenor which will generally be the missing third or fifth in the triad depending on which notes the altos and the sopranos have.
These three notes will be the triad in the root position or inverted. They are called treble voices.
However, the tenor is in the bass clef.
Duplicate the root note in the chord for the bass note.
The chord for the treble voices may be inverted. So don�t duplicate the bottom note unless it is the root.
For example, the CEG chord is in the root position so you would duplicate the C for the bass.
However, the EGC chord is inverted but you would still duplicate the C in the bass.
Make sure the voices do not cross each other.
If one note in the chord is the same in the next chord, change the other two notes to make a different chord.
Play and listen to completed phrases. Make sure each chord blends well with chord before it and the chord after it.
Change the chords if necessary so all of the chords sound well. Your ear will tell you what is correct much of the time.