How do I get a copyright on my paper?
In the United States, you automatically have a copyright in any "original work of authorship" the moment it is "fixed in any tangible medium of expression".
You do not have to register your copyright with the US Copyright Office in order to have a copyright, or to enforce the rights of a copyright holder. However, registration with the US Copyright Office gives a copyright-holder some benefits, such as inclusion in the Copyright Office's registry, and the opportunity to get "statutory damages" if your work is infringed.
You also do not have to include the copyright symbol (the circle-c, which looks like this: © ) or information about the copyright holder or date. However, including that information on the work is helpful for people reading or using your work. A common format for that information is: © Your Name, YEAR .
If you wish to make your work available for circulation, or require that people who re-use or copy your work keep your name attached to it, you can license your work with a Creative Commons or other license. One common Creative Commons license is the CC-BY license, which allows other people to distribute your work, but requires that they keep your name attached to it.