You can copy/paste the symbol from this answer © or type it as follows:
Windows
- Option 1: Hold down the ALT key, enter the number 0169 on your numeric keypad, then release the ALT key
- Option 2: In some programs such as Microsoft Word, typing (C) or pressing CTRL+ALT+C will produce the copyright symbol
Mac
- Press Option+G
References:
en.wikipedia.org/wiki/Copyright_symbol#Digital_representation
www.joyedaniels.com/keys_word.htm