Next, adjust the levels. The quickest way to access this option is to use the CTRL-L keyboard shortcut (Option-L on a Mac), but you can also find it from the menu bar by going to the top menu bar and clicking "Enhance," then "Adjust Lighting," then "Levels." A new window will open, where you'll see a graph type display, usually with a big hill or hills in the middle and some flat areas to the right and possibly to the left as well. Along the bottom are three arrows that will each slide left and right when clicked and dragged (see Photo 1).
Click the far right arrow and drag it leftward, approaching or even reaching the start of the hill (basically, you're cutting out all or most of that flat part). You'll see your picture lighten as you move the slide. (See Photo 2.)
Repeat on the left if needed.
Note: You'll notice that the middle arrow will move along with both the right and the left arrows. It also moves independently when it's clicked. Experiment with the settings until you're pleased with the result.