You just need to decide on a programming language to use. However, programming is an useful skill to have and will allow you to do more with your game design.
Unity: Unity is a popular game engine that is used to create both 3D and 2D games.The following are some popular game engines you can try: X Research source
Many allow you to download them and start learning for free. Luckily, there are plenty of game engines to choose from. More than likely, you'll probably want to use an existing game engine. If you are a skilled programmer, you can design your own game engine.
It's the software that renders the graphics, processes the sound, processes the button inputs, processes the coding and scripting, and much more. The game engine is the backbone of the game.