Head over [Crowdin][crowdin-mastodon-ios] for that. To help with translations, select your language and translate :-) If your language is not in the list, please feel free to [open a topic on Crowdin](crowdin-mastodon-ios-discussions).
1. Add new strings in `Localization/app.json`**and** the `Localizable.strings` for English.
2. Run `swiftgen` to generate the `Strings.swift`-file **or** have Xcode build the app (`swiftgen` is a Build phase, too).
3. Use `import MastodonLocalization` and its (new) `L10n`-enum and its properties where ever you need them in the app.
4. Once the updated `Localization/app.json` hits `develop`, it gets synced to Crowdin, where people can help with translations. `Localization/app.json` must be a valid json.
If there are new translations, Crowdin pushes new commits to a branch called `l10n_develop` and creates a new Pull Request. Both, the branch and the PR might be updated once an hour. The project itself uses a script to generate the various `Localizable.strings`-files etc. for Xcode.