Itch is where you host your games. To make a game you need tools like Unity, Unreal, RPGMaker, Godot, Defold or GameMaker. Give all the tools a bit of a look on youtube before you settle on one or two. I started with RPG Maker then transitioned into Unity. There are sometimes humble bundle discounts for Unity and Unreal assets too.
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Unity is free to use and both Godot and Defold are open sorce. Game Maker is free until you want to distrobute outside of OperaGX. You can get some free assets at https://opengameart.org/