This link might be helpful for you:
It's always best to educate yourself, but here is the gist of what you
need to know. Keep in mind this is NOT legal advice. An attorney
experienced in Intellectual Property can give you appropriate counsel.
Essentially, you don't have to do anything for the work to be
copyrighted so long as the work is yours, original, and falls into one
of several specific categories (which do include writings, software
and images). To be able to protect your work in any subsequent
litigation, it is wise to place a copyright notice prominently in the
work (i.e. Copyright Your Name Here 2005). Use the copyright symbol
in place of the word "Copyright" if you can. This is a capital letter
"C" with a circle completely around it. This is necessary in some
countries outside the U.S. to be considered an official copyright.
If you anticipate litigation and want to be able to subject any
copyright violators in the United States to hefty fines, rather than
simply be ordered to cease and desist in copying your work, then you
will need to register your copyright by placing a copy of it on file
with the Copyright office.