Layer Masks

Open photo

Click on Add Vector Mask on bottom of Layer Palette

Rename Layer

Choose a tool: for example brush tool.

Click on size of brush and diameter you want to use.

Switch Foreground and background colors by clicking on curved arrows in tool bar to accomplish desired effect on photo.

To add another photo-create new layer (Ctrl Shift N)

Rename the layer

Open photo you want to use

Select desired area with appropriate tool

Copy and paste to newly created Layer in layer palette

Use Move tool to move it where you want it to be.