Run flutter doctor

Run the following command to see if there are any dependencies you need to
install to complete the setup (for verbose output, add the -v flag):

flutter doctor

This command checks your environment and displays a report to the terminal
window. The Dart SDK is bundled with Flutter; it is not necessary to install
Dart separately. Check the output carefully for other software you might
need to install or further tasks to perform (shown in bold text).

For example:

The following sections describe how to perform these tasks and finish the setup
process.

Once you have installed any missing dependencies, run the flutter doctor
command again to verify that you’ve set everything up correctly.

Downloading straight from GitHub instead of using an archive

This is only suggested for advanced use cases.

You can also use git directly instead of downloading the prepared archive. For example,
to download the stable branch:

git clone https://github.com/flutter/flutter.git