dex screen options help

[jrsharp70]

I'm drawing a total blank here, need help.
There are 2 options for the tablet screen when DeX is used with an external monitor; you can show your normal tablet screen, or you can mirror dex on both screens.

I'm using microsoft office, but with the tablet in "android", I can't put office on the big screen. I need the tablet to look like the DeX interface when plugged into the external monitor.