How do I make my created 3d model a Gmod Model?

Yes, I’ve searched - nothing RELATED to the part where I make my already created 3d model (Which i made in sketchup) into a Gmod model?
A link if theres something that doesnt have a title thats obvious i missed or a laymen’s way of explaining how do I do diss.

You need to get the .smd plugin for Sketchup, from there I think you can put it in milkshape aand then export it as a half life 2 model file or some crap like that.

Grab this http://developer.valvesoftware.com/wiki/SketchUp_to_SMD_Export_plugin
This will give you an smd which you will then compile via a QC file.
http://developer.valvesoftware.com/wiki/Compiling_a_model

The problem with sketchup is that it ends up with too much terrible geometry which makes the poly count massive, the best suggestion i can make is to export to .3ds which you can then import into 3ds max and then you can get the rest of the way following magical URLs

First you need to make a Detail Model, which is the bit you can see, obviously you texture that etc etc.
After that the game related stuff, you make yourself a Physics or Collision model.

Once you’ve done both of those you’re then up to Compiling your model