Male sure you have ios and/or android platforms installed. If you are not sure go back to BUILD.md.
https://support.google.com/googleplay/android-developer/answer/186113?hl=en
keytool -genkey -v -keystore <my-release-key.keystore> -alias <alias_name> -keyalg RSA -keysize 2048 -validity 10000
Change <my-release-key.keystore> and <alias_name> accordingly also in the release.sh file:
ANDROID_ZIPALIGN="/path/to/Android/sdk/build-tools/21.1.2/zipalign"
ANDROID_KEY_PATH="/path/to/keystore/my-release-key.keystore"
ANDROID_KEY_ALIAS="alias_name"
Some Android versions can have a problem when the keyboard pops up (little hiccup of the app). If it the case on your app it can be prevented:
Open platforms/android/AndroidManifest.xml and change android:windowSoftInputMode="adjustResize" into android:windowSoftInputMode="adjustNothing".
npm run build
Then answer to the prompt. When you are done, you should have your .apk files dumped into the build folder at the project root: https://github.com/shprink/wordpress-hybrid-client/tree/develop/build
https://developer.apple.com/programs/ios/gettingstarted/
http://codewithchris.com/submit-your-app-to-the-app-store/
Sigh allow to sign .app with a provisioning file via the terminal
# https://github.com/KrauseFx/sigh
sudo gem install sigh
npm run build
Then answer to the prompt.
Once the IPA is signed, all you need to do is sending the package to Apple for review.