To make Exposure adjustments using Blend Modes you first make a layer. When you make a duplicate or copy layer it opens in Normal Mode and has an Opacity of 100% in the layers pallet. Normal Mode does not change the appearance of the image. In the Layers Pallet Layer 1 automatically becomes an active layer and the Blend Modes become active and you are able to change the Blend Mode and Opacity of this layer.
I find blend modes the most effective way to make exposure adjustments. In the Layers Pallet to the right of the word normal lick on the arrows and a menu pops up, scroll through each Blend Mode in the menu to see how they affect the image. The two I use to affect exposure are Screen and Multiply.
I selected Screen mode to lighten the image, this will usually make the image to light but by clicking on the arrow next to 100% and moving the slider to 25% for this images, I lighten the image to the exposure I want.