Install it
    
      From the terminal: Run flutter pub get.
OR

      From VS Code: Click Get Packages located in right side of the action
ribbon at the top of pubspec.yaml indicated by the Download icon.
      From Android Studio/IntelliJ: Click Pub get in the action
ribbon at the top of pubspec.yaml.

Import it
    
      Add a corresponding import statement in the Dart code.

Stop and restart the app, if necessary
    
      If the package brings platform-specific code
(Kotlin/Java for Android, Swift/Objective-C for iOS),
that code must be built into your app.
Hot reload and hot restart only update the Dart code,
so a full restart of the app might be required to avoid
errors like MissingPluginException when using the package.

Adding a package dependency to an app using flutter pub add

To add the package, css_colors, to an app: