First, stop your server
Step 1: Go to the ConanSandBox/Mods file directory 

Step 2: Upload the .pak mod file to the Mods folder using an FTP client.

Step 3: Create a modlist.txt file in the Mods folder.

Step 4: Edit the modlist.txt to load the mods.

Example
- If you have a mod file called "ConanMod.pak".
- You would add *ConanMod.pak to the modlist.txt.
- Each mod should be on its own line.

*ConanMod.pak
*ADifferentMod.pak
*AnotherOtherMod.pak