Curves isn’t exactly intuitive, so Adobe lately has been introducing tools to make it more accessible. As I mentioned in my “Introduction to Curves” post, the sliders available underneath the curve in Lightroom (and Camera Raw) to adjust brightness of Highlights, Lights, Darks and Shadows are one example of this. Another example is the targeted adjustment tool, which allows you to select tones you want to brighten or darken by clicking on those tones in your image and dragging up to brighten or down to darken. The tool detects the brightness of the tones underneath where you click, and adjusts those tones throughout your image. Click on the tool to activate it, then click and drag in your image. PS or LR will modify (i.e. bend) the curve to reflect your instruction. In Photoshop, first create a new Curves adjustment layer (Layer>New Adjustment Layer>Curves.) Then in the adjustment panel the tool is the hand with the double arrow:
In Lightroom, it is the small bulls-eye symbol in the Tone Curve Panel:
When you are done, deactivate the tool by hitting the Escape key.