You can see their ID numbers on each workshop addons URL link. Write them down as you subscribe to them in Steam. You will use the program to help you record and transfer the Steam Workshop ID numbers for each mod you want to install to your server. We recommend you have a text document on hand open such as Notepad++, if you plan on using the automatic download method. Subscribe to the workshop content you want to use on your server from the Steam client, and let it download to your PC.
Subscribe to Mods or Maps on Steam Workshop