Yes. You automatically own the copyright to any works of expression you create and it is not necessary to register your works. As copyright owner you control the use and distribution of a protected work by any other persons, whether it’s a whole work or just a substantial part. You should include a notice of copyright on your work. For all content included in each resource, you must either be the copyright owner, receive permission from the copyright owner, or ensure that the content is covered under fair use or other applicable laws. You can find more information at this link.

https://www.copyright.gov/circs/circ01.pdf