Question / Help How to make disappear the image of multiple desktop windowsduring a streaming on FB

[Bluann]

Hello, I'm using OBS for streaming to Facebook for tutorial only by my desktop, no scenes, no video etc., only my own activity on desk (browser windows, slides explanations ecc.) and my audio comment. Work it all, but I don't know how to do disappear multiple desktop windows when I switch to screen image to another. There's a setting helpful for my case? Thanks