How and Where is?
I am also wondering on how to get them to work. There are showflags for it and there are settings in the postvolume for it, but I am having a hard time figuring out how to activate them. Tried putting in r.lightpropagationvolume 1 but that didnt do anything (or at least I had that feeling^^).
So any help would be very much appreciated 
I managed to enable them. But as its a hidden feature and i got those from a epic staff message in private Betatester forum, im waiting for Epic to tell me if i have permission to make a tutorial about,for now, the betatesters are having some fun with it.
Aww man…cant wait to know 
I found a guite hidden flag on the light that says “Affect Dynamic Indirect Lighting” which sadly also didnt do anything when enabled 
I don´t want to use pre-calculated Lights process. In World Settings–>LightMass, i have unchecked Force No Precomputed Lighting. But UE4 looks as UDK, is light propagation volumes system implemented in UE4 Editor? I would like any documentation about this, but I found nothing.
Thanks
How to enable Light Propagation Volumes GI [ WIP AND BETA] - Rendering - Unreal Engine Forums Here is the tutorial on how to enable that thing