If you have written an original play, U.S. Copyright law protects your rights to the work for a period of your lifetime plus an additional 70 years after your death. During this period you have complete control and ownership over your play, and no one can use your play, in whole or in part, without your permission. Legally, an original work is considered copyrighted when it is created. But registering your play with the U.S. Copyright Office affords you additional legal protections in the event someone violates your copyright.
Go to the website of the U.S. Copyright Office at Copyright.gov. Click on the "eCO login" link on the homepage. This will take you to the Electronic Copyright Office site, which is the method the Copyright Office prefers you use when registering your copyright.
Create a new account by clicking on the "If you are a new user, click here to register" link. Complete all of the required information. When you are finished, click on the "next" button, which will take you to a new page.
Click on the "Register a New Claim" link located on the left-hand menu. This will direct you to another web page where you will then click on the "Start Registration" link. Enter all of the requested information and submit the payment required for your work by the Copyright Office.
Submit a hard copy of your play to the Copyright Office by mailing it to the Library of Congress Copyright Office 101 Independence Avenue, SE Washington, D.C. 20559-6000.