You can find a list of all registrars here.
When you want to buy your chosen .dk domain name, you must do so through a registrar.
You can always check whether the domain you want is available on our website here: https://www.punktum.dk/en/search-dk-domain
A registrar is a company that handles the registration of your .dk domain name.
Many registrars also offer a setup of your email address or website if you want to use your .dk domain name for this purpose.
You can read more about registrar management here.