Steam Workshops are available for almost all Steam games. Steam Workshops allows you to create, discover and download content to your gameserver.
This is like fast downloads, but hosted on Steam servers. You can NOT have fast downloads and workshop downloads at the same time on a game server.
1 - The first thing you need to do is create a collection of addons. Navigate to http://steamcommunity.com/workshop/ and login. Then navigate to the game you wish to create the workshop for, and click Create Collection. Add to your collection whatever you want added to the game server.
2 - The next you will need is a Steam Web API key. Think of this key as a password, you don't want to share it with others! You can register for your API key at the following page: http://steamcommunity.com/dev/apikey
3 - Now we need to add your collection and API key to your game server. You'll now want to log into TCAdmin and click the "Command Line Changer" icon. If you're using the default command line, you'll need to click the "New" button; otherwise, go ahead and click the "Edit" button to the right of your selected command line configuration. You should see two commands near the bottom relevant to the Workshop: +host_workshop_collection and -authkey. Please tick the box to the left of both commands, and for the value of the +host_workshop_collection, paste your collection ID. Similarly, paste your API key into the -authkey value.
4 - The Workshop will now be working with your server!
However, if your run custom models from Steam Workshops there is another step if you want your players to download the content from each addon. If you don't follow this step and your addon uses custom models (such as TDMcars, a custom model, etc.) then your players will see errors once they connect. To remedy this, you'll need to create or edit a Lua script so that the game mod client knows that you wish for your players to download the files. The Lua script can be named whatever you'd like, and it will be placed inside of your server's /lua/autorun/server directory. The inside of your Lua script will need to look like the following:
So, to further elaborate, let's say you added the following addon to your Workshop collection: http://steamcommunity.com/sharedfiles/filedetails/?id=104606562 Your Lua script would simply contain the following line of code:
We obtain the ID (104606562) from the URL as you may have guessed. You can see ?id=104606562, you'll simple copy that number to the right of ?id=. Unfortunately, at the time of writing, there isn't a function to force every addon in your collection ID to download, so you'll need to add each respective addon ID for this to work.
NOTE: You must use the ADDON ID in resource.AddWorkshop(). NOT the COLLECTION ID. Workshop Downloads will not work if you use resource.AddWorkshop with your COLLECTION ID.
If you have any questions or have issues, feel free to contact support.