On Thursday we answer your questions!
The Curves adjustment is one of the most popular in Photoshop CS and CC, but unfortunately it isn’t available in the same form in Photoshop Elements. It’s used to alter the tone of your picture by dragging the channels on a histogram, which makes it easy to create colour effects, as well as alter the light, dark, blacks and whites in your photo.
In Elements however, you can use the Levels tool for exactly the same edits. Open the Levels dialog by hitting Cmd/Ctrl+L and you will notice that the tool consists of stoppers along a horizontal slider. Tweak these to change brightness and exposure of your picture. Consult the drop-down menu and you will see that you can also alter the individual colour channels of your image. Now, tweak the middle stoppers for the Red, Green and Blue channels individually and you can create retro photo effects with your pictures.