If you have written a publication, you automatically have copyright in it. You don't need to do anything else for this: no registration or referencing is required. This copyright gives the rightsholder control over the publication.
The copyright holder has the sole right to bring their article or book to the public’s attention in any way, either on paper or electronically. These are the so-called exploitation rights. You can assign the exploitation rights to another party, for example a publisher, by means of a contract. You can set conditions, for example 'only for this magazine' or 'only for paper editions' or 'only in Dutch' or 'I also want to be able to distribute this myself on paper and electronically' or 'my institution may include this in a repository'.
Some higher education institutions have – or are developing – a copyright policy that sets out certain principles and a vision. In doing so, the institution wants to influence the arrangements you make with your publisher. Check the current situation with the lawyer or your institution's Copyright Information Point (CIP)