How to add workshop scenarios to your Arma Reforger server

Obtaining the ModID, Name, Version, and GameID for a mod
You will first need to download and install the mod you wish to use from the ingame workshop option.
Once installed, navigate to where the mods are installed on your PC, the default location is 
C:\Users\<Username>\Documents\my games\ArmaReforger\addons\
Open the folder for the mod you wish to set up on the server.
Locate and open the ServerData.json file
Find the "id","name","version", "gameId" options and copy the values down.
It should be at the top of the file and look like this example

"id": "591AF5BDA9F7CE8B",
"name": "Capture & Hold",
"revision": {
"version": "1.0.8",
 "changelog": "",
"dependencies": [],
"scenarios": [
{
"name": "Capture & Hold: Camp Blake",
"gameId": "{6EA2E454519E5869}Missions/CAH_Military_Base.conf"
},

Adding the mod to the server

Log in to the Game Control Panel and navigate to your server.
Stop your server
Click on the Configuration Files icon
Click on the Config Editor for the serverconfig.json
Navigate to the Scenarios option.
Check the 'Use A Workshop Scenario' checkbox
Enter in the scenario's gameID in to the Workshop ScenarioID option
It should look like this example
{6EA2E454519E5869}Missions/CAH_Military_Base.conf

Navigate to the Mods option
You would add your mod's code to this option. Each mod should follow this template

{"modId":"id","name":"name","version":"version"}

Replace the id, name, and version with the values you copied from the mod's ServerData.json
It should look like this example

{"modId":"591AF5BDA9F7CE8B","name":"Capture & Hold","version":"1.0.8"}

If you have multiple mods, include a , after each mod, except for the last one.

Example of Multiple Mods

{"modId":"591AF5BDA9F7CE8B","name":"Capture & Hold","version":"1.0.8"},
{"modId":"59673B6FBB95459F", "name":"BetterTracers","version":"1.0.5"},
{"modId": "5614E482BF83E310","name": "Sample Mod - New Car","version": "1.0.5"}

Once you have added the mods, click the Save option.