Installing Addons on a Mac/Apple Computer?

[BiohazardCoffee]

I've been placing all of my downloaded addons in /(MyUserName)/library/Application Support/Steam/SteamApps/(MySteamID)/Garrysmod/Garrysmod/addons. I have started to put them in /garrysmod/garrysmod outside of the addons folder, but they still don't seem to work.

Screenshot: [url]http://i56.tinypic.com/161m9tc.jpg[/url]
(You can see what folders I have and such)

The only addons that work for me are basically SWEPs/weapons. My ragdoll and player skins downloads don't work.
I heard you have to "extract" the folder but I don't know how?

I'm very new to GMOD so any help is very much appreciated.
My Mac is Version 10.6.6, and is running Snow Leopard.

Thank you in advance! :)