I'm following up on the comments from my last post urging (again!) the use of credit lines wherever you post/show your art.
To add a quick © to your information …
© On a Mac
Hold down the OPTION key and type the letter g.
©On a PC
If you use Windows, you must use the number pad to create special symbols. You can’t use the numbers at the top of your keyboard. So . . .
To add a © on a PC, hold down the ALT key and type 0169 on your number pad.
Update: You can also use Ctrl+Alt+c on a PC, which seems to be the easiest way (thanks, Michael!).