Photoshop :: Tinting Shadows With Gradient Editor?

I recently saw a presentation that spoke of tinting shadows on an image by converting to black and white, then creating a gradient map layer.  From there you went into the Gradient Editor and place the cursor directly beneath the gray scale, and starting from the black end, move it toward the white end until the arrow cursor changes to a finger pointer.  You then use the value in Location...
 
Unfortunately, every time I do this my cursor is ALWAYS a pointing finger.  I can put in color stops, but I don't believe that was what the technique used...  I've tried using alt, ctrl, and/or shift in all the combinations I can think of, but no matter what I do, I always get the pointing finger instead of the arrow cursor.
 
what I need to do differently to get the Gradient Editor to show an arrow cursor until I reach whatever point I should be at when it changes to a pointing finger?  Does it represent the darkest black in the image, or what?