This is probably explained in 100 different places, but how to change the texture of a certain area? Like making a mountain stone, but the rest of the map grass? Thanks in advance!
Do you mean that you have a landscape and you want to paint on to it with different textures?
(first minutes)
Ok, saw you 2nd thread in the rendering section. I will close this one now 
https://forums.unrealengine/showthread.php?8658-Changing-the-texture-of-a-certain-area