Hi. I have no even an idea how to make it. How does dlc get’s integrated into a game, how do I just paste it inside it, how does a game works without dlc. Please give me some idea on how this works! Thanks 
This one is very important for me please help
The DLCs are like plugins, I suggest you to see the UnrealFrontend interface for packaging DLCs. If you want to implement DLCs in a multiplayer game, maybe with Steam, things are a bit different, but in singleplayer games this system should be enough.