Hi,
These options are hid under the names of Adjust Color Curves or Adjust Color Levels. Try to find a horizontal bar of sort or histogram with three small triangles under it representing white, black and gray (middle) tones. When you move such a triangle towards the black area in the histogram graph you should see the results on the processing image. What results depends on what do you do with those "triangles" (aka slider hooks).
I made two images with "white hook" two positions in Adjust Color Level window. Search for similar options in Elements 9. I didn't change the size of the two screenshot files.
Regards