There is quite a lot of information about copyrights available on the Internet. To use copyrighted work you will need permission from the holder of the copyright. You do not always have to pay for permission. If your work is useful, often you can get permission to use the material at no cost. They will tell you the conditions that apply.
Copyrights are automatic.
You don't necessarily need to register your work anywhere. You do need to indicate clearly that the work is copyrighted. Here is one tip about copyrights, well known to authors and musicians. Do not open the envelope when you get your own letter back. This should provide you with sufficient evidence in the case of a dispute.