To add mods on your DayZ Standalone server you will want to do the following:
Switch your servers map type to "Custom" via the Game Server Control panel to enable the "Custom Launch Parameters"
Upload all of the workshop mods you wish to use on the server via FTP to the base directory (Or add the id(s) of the mods to the Mod ID area on the panel to have the server download them for you)
To activate the mods you will want to put -mod= followed by the mod you wish to activate
For example -mod=@example;@mod;@folders
Note: if you have mods with spaces in the name. Add " " around the -mod=@example;@mod;@folders part
It is important to note that if the workshop mod comes with a "Keys" folder you will need to add the file contained within that folder to your servers main "Keys" folder in the main file directory if not already there!
Then click on the green "Save Settings and Restart Game Servers" button for the changes to take effect and for the mods to load!
Once the server is fully booted up and shows started (You may need to refresh the page) head to: https://dayzsalauncher.com/#/servercheck and enter your servers ip:port number (change the last port number to an 8 ) and click check server. This will add your server to the dayzsa launcher and allow it to show the new mods you have added.
To edit/upload/save/delete files via FTP, use the following method:
Stop your server from the panel.
Log in to FTP using WinSCP (a free FTP software) using the connection details found in the "FTP Details" section of the game server control panel. Download link for WinSCP here: http://winscp.net/eng/download.php
Navigate to the directory you wish to upload or edit a file.
After editing/uploading/deleting your files in the proper directories, start your server from the panel.
If you run into any issues with this method please let us know and we can provide you with a price quote to have our staff install these mods for you