It`s very interesing and quick lesson. Let`s start:
1-Use Gardient Tool to create background or Press G.
Note: you can use also print tool too.
2-Create background as you like and I did this.
3-Choose any image you like, I chose Cloud`s image.
4-Move Cloud`s image into background image.
5-Go to Luminosity.
Finally,the image will be like this

Here are the samples of our lesson: