You don't say what hardware system or software you're using etc, so it's a very open ended question. If you're using windows the simplest way to guide you is to look for an application which is on all windows operating systems called "Character Map". It will show the copyright symbol and allow you to copy and paste it wherever you want to use it.
on Windows XP you'll find the Character Map application by clicking on Start, then Accessories, then System Tools then Character Map.
You can also obtain it by using a key sequence, typically typing 0169 whilst holding down the ALT key.
