Live video streaming in UE4. How to use this great plugin ?

Hi guys,

I’m new in UE, I come from the VFX field. I’m tring to do real time chroma key in UE4 like this:

But with live video feed from a blackmagic capture card with this plugin:

The plugin come with no explaination or tutorial. could someone explain to me how to use it with the media player ? How do I use the stream from the decklink as a source ?
Thanks a lot.