I adjust the Levels first by sliding the right slider over until it meets the first bit of black on the graph. Then I adjust the Curves by pulling the middle of the curve up to brighten them. Then, I'll add a Surface Blur to smooth out the skin. And last, Unsharp Mask to make everything sharper. Sometimes, I'll have to go and up the Saturation or the Contrast, but usually I just do Levels, Curves, Surface Blur, then Unsharp Mask

I do hope that made sense.. This is what I got by using these steps on your siggy. (which is super cute by the way) I'd normally play with it more probably until I got it more sharp, but I don't have a ton of time lol hopefully, that helps you out, though!