The copyright owner decides if another can make use of their rights, by granting permission or licensing some or all of these rights.
You don't have to do anything to have the protections of copyright; once your work is fixed, you automatically gain these rights. Publication of the work is not required, nor formal registration, nor inclusion of a copyright notice.
Employers usually own the works created by their employees in the course of their job, and commission works (works for hire) are usually owned by the person or company that commissioned them. Virginia Tech intellectual property policy states copyright for traditional works of scholarship (articles, books, and artistic works) created by Virginia Tech faculty are owned by that faculty member. (Other products of scholarship, such as patents, are treated differently.)
Adding a copyright statement (the word copyright or the symbol © along with the name of the author or creator and the date of creation or publication) can help make your ownership clear.
Registration with the US Copyright Office can offer some legal benefits in case of infringement. You'll pay a fee and need to deposit a copy of the work.
You can choose to license your work to others. Virginia Tech authors have several cases where licensing is required: