How to make a 2d game?

[CroKing]

I want to make a side-scrolling rpg with a real time battle system, similar to this series - 勇者之路 (Sorry I think it's in Chinese, you may find some images of it on google). I have a pretty good understanding of C++ but I've never tried creating a game like this. I know to create a game, I need a game engine. After some research, I've decide to use a preexisting one. So my question is which one should I use and since my game is in 2D, I should learn SDL, right? Is this even the proper procedure? Please don't use any programming jargons. If anyone has previous experience or a knowledge on this any help will be appreciated.