1. Open your file
2. Choose Windows/Layers to ensure your Layers palette is visible.
3. There is an arrow in the layers palette that will enable you to create new layers and duplicate layers. This enables you to "build" a montage of images. Select the arrow to view layer options.
Choose Duplicate layer, press ok. This produces a duplicate of the background image. This is helpful when you want to preserve the original.
4. Click on the Eye in the layer palette for Background layer. This turns the background layer off making it invisible. Click in the square again to turn the layer back on.
Add Elements
5. Open file #2. Using the move tool in the tools palette, drag the woman into the your photo. (See 1st link below and follow the additional instructions.)