There are a number of ways you can do this. For the best effect I would put that layer on like Darken or multiply over another background. If you just want it cut out, you can use the lasso tool to select places and then delete them. The pen tool (basically do the same thing and then make a selection out of the path). Magnetic lasso tool, magic wand tool, background eraser...so many ways.
Google search how to render and image. However if you just play around with the tools i mentioned you should be able to grasp the idea quite easily.