Sorry if this is posted elsewhere. I'm sure this is an easy task, but I can't seem to get it to work.
I have a CAD file from a client, which contains a bunch of superfluous construction geometry. But that geometry is also expressed as a bunch of needless layers in the Browser window. I'd like to delete all of those, but it doesn't seem as simple as just clicking on a layer name, and hitting "delete". What am I missing here?

Thanks so much!