How to lighten pics?

I've searched through the memories and didn't see an answer to my problem and so I'll ask for help on it. I'm working with screen caps that are very dark. The background was dark and so was the clothing. I've tried lightening up the image and it's just not working.

I'm using PSP 8 but I also have PS7, where I am completely clueless as it's new. It seems that I was able to adjust dark pictures pretty easily in PSP7, but 8 isn't letting me do it.

Is there a tutorial for either of the programs? Or can someone help me here? Thanks!