Correct README.md for experimental multiplatform template (#2795)

experimental/templates/multiplatform-template/README.md

@@ -1,8 +1,70 @@
-Compose Multiplatform Application
+# Compose Multiplatform Application
 
-**Desktop**
+Сan run on desktop, Android and iOS.
+Note that iOS target is experimental so far.
+
+## Desktop
+This template contains 'desktopApp' run configuration that you can use to run the desktop target in Android Studio or Intellij IDEA.
+
+Useful Gradle tasks:
 - `./gradlew run` - run application
 - `./gradlew package` - package native distribution into `build/compose/binaries`
 
-**Android**
+## Android
-- `./gradlew installDebug` - install Android application on an Android device (on a real device or on an emulator)
+To run on Android, use `androidApp` run configuration in [Android Studio](https://developer.android.com/studio)
+or use Gradle:
+
+`./gradlew installDebug` - install Android application on an Android device (on a real device or on an emulator)
+
+## iOS
+
+To work with the iOS target you need:
+- [Xcode](https://developer.apple.com/xcode/) (to setup the environement)
+- [Android Studio](https://developer.android.com/studio)
+- ["Kotlin Multiplatform Mobile" plugin](https://plugins.jetbrains.com/plugin/14936-kotlin-multiplatform-mobile) (to work with all supported targets, including iOS)
+- [CocoaPods](https://kotlinlang.org/docs/native-cocoapods.html)
+
+Before trying to open the project in Android Studio, make sure that you have a correct environment for iOS development. 
+Try to follow official Apple tutorials how to create a sample project in Xcode 
+and register a simulator or a real device there.
+
+### Running on an iOS simulator
+
+If you have a correct environment, Android Studio will show available iOS simulators on which you can run the application
+in `iosApp` run configuration.
+
+### Running on a real iOS device
+
+To run on a real iOS device you need:
+- [Team ID](https://developer.apple.com/help/account/manage-your-team/locate-your-team-id/#:~:text=A%20Team%20ID%20is%20a,developer%20in%20App%20Store%20Connect.)
+- set this Team ID in `iosApp/Configuration/Config.xcconfig` in the `TEAM_ID` field
+- the registered iOS device in Xcode
+
+After that you can open the project in Android Studio, and it will show the registered iOS device in `iosApp` 
+run configuration.
+
+**Hint:**
+If you use a free Personal Team for signing applications to run on a real device, 
+and you do not have access to the link above to know your Team ID, you may still find your Team ID value,
+using the following workaround:
+- manage to run a sample iOS project in XCode on a real iOS device 
+- open XCode project in a text editor and search `DEVELOPMENT_TEAM` substring in it
+- the value of `DEVELOPMENT_TEAM` property is your personal Team ID
+
+
+### Configuring the iOS application
+
+This template contains `iosApp/Configuration/Config.xcconfig` that allows you to configure the most basic properties, without using Xcode. It contains:
+- `APP_NAME` - target executable and application bundle name
+- `BUNDLE_ID` - [bundle identifier](https://developer.apple.com/documentation/bundleresources/information_property_list/cfbundleidentifier#discussion)
+- `TEAM_ID` - [Team ID](https://developer.apple.com/help/account/manage-your-team/locate-your-team-id/#:~:text=A%20Team%20ID%20is%20a,developer%20in%20App%20Store%20Connect.)
+
+Note, that to configure the `APP_NAME` setting, you should open `Config.xcconfig` in any text editor *before opening* the project in Android Studio and correct respective value.
+
+If you need to change this setting after you open the project in Android Studio, please do the following:
+- close the project in Android Studio
+- run `./cleanup.sh` script in a terminal
+- correct the setting
+- open the project in Android Studio again
+
+To configure advanced settings you need to use Xcode. Open `iosApp/iosApp.xcworkspace` in Xcode after opening the project in Android Studio.