Go to Google.com type in "Photoshop *Version you use* Brushes" and browse some sites that have brushes. You download Brushes and then load it into Photoshop. So just go over the Internet and search for some good brushes, pictures are shown and details are given. Once you have downloaded them, they are probably 256 Kb or around 1Mb, not much. Then after the download, unzip the file, and load it into Adobe Photoshop by click on the Brushes menu and then going to "load brushes" and that's it, they are used to apply effects on your pictures.