Using the Rectangle Tool (U), represent a vertical stripe along the background’s left side.



The layer’s parameters:
Fill 0% on the layers.
Opacity 30%
Blending Options>Gradient Overlay



Gradient’s parameters:





Make a copy of the recently made layer and select the Free Transform option to turn the copy over and place it the way it is indicated below.





Select again the Rectangle Tool (U) to divide the background in two halves.