Hi Letha I do not think the different positions are changed so much for the type of song you are singing. It is more for adjusting the sensitivity of the mic for the volume strength of the specific application IE vocal, guitar amp, other instruments.

My advice would be to experiment with the different settings to find the one that gives a clear signal without distortion.
Colin is correct you do not want levels to be above the halfway marks or very low peaks. Go for peaks just touching the .5 mark.