Screen sharing mimics exactly what's on your screen, so if you only have one screen and you have Virbela open, or you have multiple screens but share the one that has Virbela on it, the presentation board will look something like pictured above.
If you run into this issue, you can try a few different things depending on your setup.
1. If you only have one screen you can choose to open Virbela up in "Windowed" mode. You can do this by closing and opening the Virbela app, and making sure that " Windowed" is checked
This will give you the ability to setup your screen sharing with Virbela, and then minimize it like any other program so other people can see your screen. The only downfall to this is that you will not be able to see what's going on within Virbela while you have it minimized. You can also try uploading your documents straight into Virbela as detailed in this guide
or using Google Docs
2. If you have two screens, make sure that Virbela is running on your secondary screen, or if using CrankWheel, choose the screen that does not have Virbela on it.