Help with uv mapping

I am new to modelling for games, and I have just successfully created my first prop, kinda (yay) It took me ages to work out all the compiling business from tutorials but the only one thing I cannot grasp is texturing. The model comes up with the pink and black missing texture texture when I place it in gmod. I am using Google Sketchup with the valve plugin to create my model but I cannot find a way to uv map it, and I’m not quite sure what uv mapping is either, so any help or a tutorial (ideally) would be great with this, thanks =]

you could import your model into blender and do the uv map there
there are countless tutorials on youtube on how to do uv maps in blender

The $cdmaterials line of your .qc has to point to the folder that contains the model’s textures, like this:

$cdmaterials "models\Humans\Male\Group01\"

If that’s not established, your model will appear with black/pink chequerboard textures.

I don’t know what Google Sketchup is capable of UVW-wise, so your best option may be Blender, like Hanibal said.