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 documentation it says that option to do this is under tools menu:

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

In BSP category advanced drop down (down arrow at bottom of category) in 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 GUI? I have same error, but cant find it in Mode selector. Is BSP advanced editor available off of Geometry Editing Mode?

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

5545-cleanbsp.png