First Right Click on the part you want to change the material on and select Unlink Material from the pop up menu.
Then double click on the part to activate the Material tab for that part.
Next select the Textures tab in the Material properties panel.
Finally select the Move Texture button which will bring up the Move Widget that allows you to Scale and Rotate the texture to meet your needs.
You may want to go over to then KeyShot web site and spend some time in the
Quick Tips and Tutorials section.