Learn how do create a complete Wallpaper Project. Open a new file with
800x600 px and
72 dpi. Apply the here shown instrument in two stages

to create the primary background’s layer. First we have to represent the right half and then by copying and changing the parameters we have to represent the left half.

The parameters for the right half:
Blending Options-Gradient Overlay
Gradient’s parameters:

The parameters of the copy situated on the left side:
Blending Options-Gradient Overlay
Gradient’s parameters: