Help with tuning?

I am having a devil of a time tuning my new Dulcimer. It’s a McSpadden Ginger model, D-A-dd.  I have an ordered an  Snark electronic tuner . for now I’m using the fender tuner app on my iPhone or trying to use my ear.  Mostly, I’m just getting frustrated and also I’m afraid I might break a string. Suggestions anyone, everyone.  THANKS