Can't add addons

I am useing scrds for hosting a gmod server, and I can join my own server, but when I try to add addons to the server, it isnt there.
Can I just make a addons folder there, or do I have to put them in to lua?

No, the addons go into the addons folder.

Make sure the addon you downloaded contains a ‘info.txt’ in the main folder. If so, put it in addons. If that fails, try updating server content. Or if all else fails, DELETE the srcds folder. And redownload all the content.

<Server Root>/orangebox/garrysmod/addons

If the file isn’t there, you have srcds setup incorrectly.