watermark issues

I have created a watermark and would like to use it on my photos.  The issue I am having is that the brush is in the detail smart brush column.  I choose my default brush with my watermark logo and hover over a photo I would like the watermark applied to.  However, when I click on the photo, whatever preset is highlighted, gets applied with a new layer.  How do I apply just the watermark without it making up a new layer with no watermark on it?  So confusing, what am I doing wrong?