Hello Toshi9003,
To activate the mods on your server once uploaded, navigate to your Giants Farming Simulator Interface and at the top you'll see a menu, select "Mods" here and you can click the blue arrow next to each mod to install it and activate it to the server.
IM sorry kinda new to this but I have uploaded mods but I can see how activate and dont what heck Giants Farming Simulator Interface is. Can you help me under stand.