Before getting too into it, be aware that Godot 4's web exports have compatibility issues with players using macOS or iOS even though they're playing on web from their browser, while Godot 3's web exports work fine on anything. You can still make non-web exports for mac or iOS with Godot 4 that run fine if the player installs it. But if your goal is to make web games for NewGrounds then you might want to stick with the latest release of Godot 3, and use the GLES2 renderer since it'll be the most compatible with anything even if the player is using a potato.
Start with the Godot Docs and change the version in the bottom left to be whichever Godot 4 or Godot 3 version you're using and start there. At least go through their Getting Started section and explanations on how things work and bookmark that site because you're going to be referring to it a lot. And read whichever parts of the Manual section look like they would be relevant for you. Afterward, if you like videos then I'm sure there are a bunch of youtubes on it, but I personally hate videos and wrote this text tutorial walking through everything I did to make a small gamejam game that covers a lot of the fundamentals using Godot 3. And you're probably starting from the right place if you already have a game in mind and can, as you're reading stuff, pay attention to what people are doing and why so you can identify what approaches you can use when you're making your own game (or decide you want to change plans to make things easier).
If you have some coding experience and are familiar with variables and types, if-else, for() loops, functions and passing parameters, and are sort of familiar with object-oriented principles then you're in a good position to start. Otherwise it might be kind of tough and you might want to focus on learning some coding outside of a game-making environment first, like learning some Python or C or JavaScript or smth. It doesn't really matter which exact language you learn as long as you get the concepts down.