I have two tutorial hubs on the forums for C++!
#Assorted and Advanced
http://forums.epicgames.com/threads/972861-36-TUTORIALS-C-for-UE4-gt-gt-New-Algorithm-Analysis-Obtain-Animated-Vertex-Locations
#Basic Core Concepts
http://forums.epicgames.com/threads/973803-19-Tutorials-Entry-Level-UE4-C-Overview-Making-Your-Own-UE4-Operators-(FString)
#Where to Start
You need a place from which to operate, I use the Player Controller to do huge amounts of stuff
You could also use the game info class or the game state class.
Pick which class you want to put most of your code in that will modify the world, and then you should blueprint that class.
Then you need to modify your game info / game mode class to use your custom class which you create in the c++, for either player controller, game mode, or game state
Some of my earlier tutorials in the Assorted tutorial hub will help you with this, I show how to do this process for the HUD class.
Once you have your custom controller/game mode /game state class, then you can begin thinknig about how to get references to objects you place in editor or spawn at runtime.
#Small Request
I would request that you make future concerns (that are c++ related) into separate threads and leave this one checkmarked so as to separate the topics out for future searches people do on the UDN
Rama