Hi Becky. Yes it is a little dark on my screen. Try the Curve command. Lift the centre of the curve up to brighten the mid-tones in the image while leaving the black and white ends unchanged.
Ordinarily I'd do it Peter's suggested way, but in this precise example; I would actually be tempted to artificially darken, or even clone out, the background highlights that are causing the mis-set white point, then raise the exposure.