You don't want anyone stealing your work. One way to prevent that is to add a copyright notice to your image. You can do this easily by creating a custom brush in Adobe Photoshop to paint the notice into any image at any time. You can even resize it, change its opacity, and use layer effects to add things like drop shadows. When you get the hang of it, use this same technique to store a logo or any other watermark.
1. Open a new image by going to File> New. Any size will do, as long as it's not tiny. Then choose the Type tool from the toolbar or get it by typing T on your keyboard. Click on your image to start typing (this will automatically put your text on a new layer).
2. To make the © using a PC, hold down the Alt key and type 0169. On a Mac, press Option + G. Then type in a copyright notice (your name, your company, etc.) as you want it to appear. Pick a font you like -- you'll be stuck with it.
3. Now hide the Background layer. Do this by clicking the eye icon to the left of its name. Make sure your Type layer is still selected (click on it if not). Then select your text: Go to Select > Color Range, move the Fuzziness slider all the way to 200, and click OK.
4. Then make your custom brush: Choose Edit > Define Brush Preset. Enter a descriptive name for the brush (like MyCopyright), and click OK.
5. To use your new brush, select it. Grab the Brush tool (type B). Then, from the Options bar at the top of your screen, pull down the Brush menu and scroll to the bottom. Select the one you made, and stamp your copyright anywhere you want.