Choose File > Place, browse for the background image file and click OK. The image should be placed into Photoshop as a new layer with a transform box allowing you to resize the image. Resize the image so that it its into the document boundaries. When resizing, hold the shift key to main the image aspect ratio.
Move the layer to the bottom. We've just masked an image, but wait we're not done. Look at the image below. The hair still has a red outline and near the legs (not shown in the picture), it has a red glow. This was caused by the drop shadow in the original image. In the next steps, we'll work on fixing this issue and working on the hair.
Step 9 - Use the Levels tool to shrink the mask.
First, zoom into an affected area with the glow. Select the layer mask then open the Levels tool (Image > Adjustments > Levels). Move the middle slider towards the right until the edge glow disappears.
Photoshop Tutorials 
