1. Here's how to adjust the levels of your image. Select Image, > Adjust, > Levels or just press Ctrl+"L" on the keyboard as a shortcut.
2. After selecting the Levels option, a small window will appear like this. Note that I maximised my art and pressed the 'Tab' button to make the tools and other windows disappear. 3. On that small window, adjust the Input Levels by dragging the black triangle on the left and white triangle on the right of the graft closer to each other. The image above is my usual adjustment. You can try your own. I'm not going to touch on the Output Levels and options just yet, so you can ignore them for now.