This guide is a simplified setup on Flutter’s official page. There is no extra step that is not on Flutter’s official page. The reason I do this is to provide you with a more efficient and secure installation guide.
First of all, you need an Integrated development environment (IDE) for flutter. You can use Android Studio or Visual Studio Code. Since Visual Studio Code works more efficiently, my importance to you will be to install Visual Studio Code. You can download from this link. (Make sure you choose the apple silicon version as we are installing for macs with m1 chips.)