Object Error,Please help im new

Well I just got gmod but I don’t know how to install add-ons. I viewed some youtube vids, went threw it exacly how they did but my add-ons STILL didnt show up.
Some other questions:
1.How do I get rid of the big red error message that are on some objects go away and show the actual object?
2.I downloaded something off the duplicator list but the machine guns arent working, any fix for that?
That is all.
Thanks for any help!(

Give some more information… like what gives errors and the addons, where you placed them? what addons? And maybe the problem is bad internet…

The things I am getting the red errors on is stuff from the duplication list. Its most things on the list I get red errors from. For the add-ons I just cant find the tab ingame to use them…I know I installed them in the right place I just dont know how to find them ingame.

So let me get this straight:

You wanted to dupe something like “sexy samus pose” or “C00l miranda hot pose” and you can’t see the models for them right?

[editline]3rd January 2013[/editline]

Well those are poses, and don’t come with the models. You’d need to find where the models are actually stored. The dupe just takes that model and poses it and dupes it; it’s just the pose itself, not the model.

I changed my first post with some new questions if you guys can tell me the answer to any of this I will be very happy.