this is the method I use to brighten up and enhance my photos.
I have circled in red what we will adjust. simply drag an area of the line upwards, to make it look like this --
you can play around with that until it looks good with your photo. make sure to click OK! here is the after of mine --
you can stop here, but I'll show my next step...
go up to Filters > Enhance > Sharpen --
you can adjust this as well to your taste, I usually put it around 35 or so, depending on the particular photo.... click OK and you're done!