How do you run Clean BSP Materials?

I’m getting a warning when building my lighting saying: Run ‘Clean BSP Materials’ to clear N unnecessary material references. Looking in the documentation it says that the option to do this is under the tools menu:

However, I can’t find any tools menu! Am I being a tool? Where is the menu/option?

In the BSP category advanced drop down (down arrow at the bottom of the category) in the details panel you can find a button that will do this.

Is there any chance you could throw up a screenshot showing where this is in the GUI? I have the same error, but cant find it in the Mode selector. Is the BSP advanced editor available off of the Geometry Editing Mode?

With your geometry brush selected, look in your Details panel and scroll down to the Geometry section. Expand it by clicking the down arrow.