There are a couple of ways that you can selectively brighten an area in Photoshop. One way is to use the Dodge tool. To do this, you will need to set the Dodge tool to Highlights and then paint over the area that you want to brighten. Another way is to use the Brightness/Contrast adjustment layer.
To do this, you will need to create a new Brightness/Contrast adjustment layer and then increase the brightness until you are happy with the result. You can also use a Levels or Curves adjustment layer to selectively brighten an area. To do this, you will need to create a new Levels or Curves adjustment layer and then drag the white point up until you are happy with the result. Finally, you can use the Exposure adjustment layer. To do this, you will need to create a new Exposure adjustment layer and then increase the exposure until you are happy with the result.
So, there are a few different ways that you can selectively brighten an area in Photoshop. Which one you use will depend on what you are trying to achieve and your own personal preference.