I thought that it might be in usr/library/application support/sketchup but it's not there. Should it be there? Or elsewhere? I have no textures anywhere to add.
Roger, here's some screen grabs off my Mac version of SU.
There's a brick icon at the top of the Materials window. Click on that. Then click on the little up/down arrows to the right of where you see the word 'Metal' in this view.
You should get a list from which to choose your materials. It won't be as long as mine but you should have something.
I don't even see a Materials window. I can see Materials in the ....doh! Being obtuse...I missed the icons at the top..thought it was just a colour wheel. Thanks!