Use a brush to "paint out" the portions of the image that should disappear. The mask itself is white, so it is easy to remember that "white reveals and black conceals". Use a soft black brush to paint out the background.
Beginner Photography Tutorial - A step by step guide on how to blur out the background in your images! Learn how to pull focus to your subject in this guide for beginners. You can also get your hands on a free "cheat sheet' so you can print out the steps
Learn how to create a watermark to protect your photos with this Photoshop Tutorial. Quick & easily create a transparent watermark to use over and over again. Tutorial complete with step-by-step instructions with photos.