Just follow this link : https://flutter.dev/docs/get-started/install
And follow each and every step
How can you install Flutter?
Operating System Windows 7 or Later (I am Windows 10. You can also use Mac or Linux OS.).
Disk Space 400 MB (It does not include disk space for IDE/tools).
Tools
1. Windows PowerShell
2. Git for Windows 2.x (Here, Use Git from Windows Command Prompt option).
SDK Flutter SDK for Windows
IDE Android Studio (Official)