There are various copyright laws based on the type of content you want to copyright. The first step would be to visit copyright.gov to learn about the types of copyright laws and which law and process is right for you. Some things are protected by copyright laws as soon as they are in tangible form. If you believe you have a case against someone that has violated your copyright, you can contact the government copyright office.
It is easier to prove you created something before someone else if you register your content. You can do this online or through the mail.