Resource.Addfile Help. Can somebody explain to me how it works?

I made a Gmod server and I have fastdownloads enabled.
I want to have a certian weapon on my server.
The files are in the addon folder AND in the materials,models,sound and resource folder.
It’s also all on my FTP.
The problem is,is that when I join the server it doesn’t download the files from the materials models sound and resource folders.
Accoarding to this guide:

You have to use Resource.AddFile.
Now I googled everywhere and I still don’t understand how that works.
Can somebody explain he step by step how to do it?
Do I need to make a certian file? Is it a command for my server.cfg? I don’t understand.
Also,can I make people just download all the folders with this command?