How to make Bulding System like The Forest/Fallout 4?

I want to make bulding system that’s exactly like the forest or like this video Unreal Engine 4 "the forest" like building system, updated for 4.9 - YouTube where you place an uncompleted alpha object and you find resource to fill in to completly build it, also i want to keep it restrict the area kind a like Fallout 4 where player can’t bulding things messing around but just only on their allowed area (All in blueprint)

Since i dont want to buy this stuff instead wanted to learn and make it myself please guide me how to do this!

Thank you

hello anyone???