You as the owner do not need the DLC, because the mission files come with the server.

Switch to an official map

1. Stop the server in the panel .
2. In Files, open serverDZ.cfg.
3. In the Missions section, change the template= line, for example template="dayzOffline.enoch";.
4. Save and start the server.

Add a custom Workshop map

1. Find the map’s mission folder on its Workshop page or readme. It is usually named like empty.mapname.
2. Stop the server and upload the folder into mpmissions.
3. Install the map’s terrain mod the same way as other mods, see mods.
4. Set template= to the exact folder name, capitals included.
5. Save and start.

If the server will not start, check the template= spelling and that the folder exists in mpmissions. Players also need the map mod installed.