Camping-Sites-in-Denmark.dk does NOT provide a central booking system.
You need to please contact the camping site where you intend to spend a weekend and/or your camping holiday. All camping sites are registered under their Company Name, Address, Zip/Postal Code, City, and Phone Number, as a minimum.
The camping sites linking to their own websites probably have links to their own booking systems under both their company and renting profiles at Camping.dk.