Lee, it's difficult (for me) to understand what you are doing, but in principle if you want to apply harmony to just one voice part (ie. the most popular option) you set it to whatever voice part you want, Right1, 2, or 3 as Eileen wrote and ignore the other voice parts (as far as harmony is concerned). You can either turn the latter parts off or have them accompany the Harmony part in unison, in which case their volumes need to be set appropriately.
If you want 2 or 3 voice parts to all play in Harmony together (a bit like Ensemble does) you select Multi from the cog wheel settings along with harmony volume and set the individual part volumes apprpriately.
PS have just seen Panos' suggestion--good point
Harmony is one of those I leave ticked all the time.
John