Maps don't work help?

Well i have downloaded Halo ODST maps and put them into Steam>Steamapps>Myname>garrysmods>garrysmods>Maps
But they don’t apper in map part when you start it.
I am slightly new to this by the way sorry.

They’re most likely fake.

But am i putting them in the right place?

That is the right place. Are you putting the bsp files in there?

Well you should extract the .bsp files into the maps folder, if they end up in a folder in the maps folder (like /maps/maps) then they won’t work. You should go into your garrysmod/maps folder and make sure they are in the right place.

How do you extract the files ?
Is there a program for it?

Winzip, WinRAR, 7Zip, there are quite a few programs for file extraction.