Go to the Filters section and select Other and High Pass.  This will get you to the High Pass Filter.  Choose an edge and adjust the radius to a different sharpness.  The usual sharpness is between 1.0 and 3.5.

Go to Layers, New Adjustment Layer and Levels.  Select Options where you will see three buttons.  Test all three buttons to find which one will provide you with the best colors for your image.

Go to Layers, New Adjustment Layer and Curves to set the image’s contrast.  To form the shape of the letter S, click about ¼ of the line upward and pull the image down just slightly.  Then go about ¾ up the line and pull up slightly.

Make new layers on top of everything shown.   Use the Overlay command and the brush tool.  Change the colors back to black and white.  The flow should be around 30%.  Set the hardness at 0% in the brushes palette.  Paint the selected areas that you want to draw attention to in white and black.