How to provide DLC?

Im developing different games and most of them I would like to release DLC for them. Im totally unsure on how to do this and I heard that nothing can be imported externally. How do I get this kind of thing into my games?

This is no easy task! The best solution I can give to you as a new guy (I assume your new to unity and coding you might not be apologizes if your not.) Is just to the give the DLC’s as separate games. But if by DLC as in adding new weapons and maps or things like that you may run into trouble. I recommend find a freelance coder on the forums to help out. Cause this probably is gonna cost you.