Mac
Use the following instructions for macos:
Start Android Studio.
Open plugin preferences (Preferences > Plugins as of v3.6.3.0 or later).
Select the Flutter plugin and click Install.
Click Yes when prompted to install the Dart plugin.
Click Restart when prompted.
Linux or Windows
Use the following instructions for Linux or WIndows:
Open plugin preferences (File > Settings > Plugins).
Select Marketplace, select the Flutter plugin and click Install.