How to make levels in Photoshop.

The very first thing I did after choosing the pictures I wanted to work on was to duplicate the images.

1. Then I had to decide which is going to be the background, and which the overlay. The background is always the starting point and other pictures go onto it.
2. To move the picture onto the background i have used the move tool. I have clicked onto the overlay picture and drag it on the top of the background picture. It appeared in the background layer as 'Layer1'.
3. Next thing to do was to create a layer mask and use 'reveal all'.
4. I had to click on the paint brush and choose the right size from tool bar. I needed to make sure that the 'layer1' is highlighted when I wanted to make changes to it and then paint away with brush. This means getting rid of the overlay I did not want to use. To bring back the overlay I needed to switch the colours on the paint buckets, so the black would overlay the white bucket.
5. When I was sure that I have finished working with the images I needed to merge all the layers.

This is an example of my multiple image: