1. Replace the non-translated string in the codebase:
```
Text("Hello world"),
```
with a method call:
```
Text(I18n.of(context).helloWorld),
```
And add the method to `/lib/i18n/i18n.dart`:
```
String get helloWorld => Intl.message('Hello world');
```
2. Add the string to the .arb files with this command:
```
flutter pub run intl_translation:extract_to_arb --output-dir=lib/i18n lib/i18n/i18n.dart
```
3. Copy the new translation objects from `/lib/i18n/intl_message.arb` to `/lib/i18n/intl_<yourlanguage>.arb` and translate it or create a new file for your language by copying `intl_message.arb`.
4. Update the translations with this command:
```
flutter pub run intl_translation:generate_from_arb \
--output-dir=lib/i18n --no-use-deferred-loading \
lib/main.dart lib/i18n/intl_*.arb
```
5. Make sure your language is in `supportedLocales` in `/lib/main.dart`.