Transfer GMod

ok, i wanna play GMod on my new Desktop PC (because it has a better video driver then this crappy old lap-top) But my NEW PC does not have internet! (long story short: i cant get my internet hooked up to my new PC to save my life!)
So, im wondering how i can Transfer GMod from my lap-top to my new PC.
any ideas?

Start steam in offline mode and back up your files.

Plug in an Ethernet cable to your PC and to your Router…

That the problem, i do that, but it still does not work.
somethings like, really wrong with it.