How do I go about copyrighting model sheets, or character sheets?

Model sheets are character sheets- sheets cartoonists use to help draw characters from different views and expressions, poses, etc. They can be copyrighted:

http://en.wikipedia.org/wiki/Model_sheets

Copyright and fair use

Model sheets are not typically in the public domain, but are copyrighted material owned by the animation studio which created it. There used to be a lot of model sheets on the internet, however many[who?] studios demanded that they be taken down.

Although model sheets originally are intended for artists who work for the studios that own the characters for which these templates are developed, other artists, such as those who create fan art, profit from them by adapting their characters to their own uses. In addition, parents often download and print model sheets as free coloring books for their children.

How do I go about copyrighting them? Do I register them for copyright with the Library of Congress? Please help-thank you.