Watson is not recommended. It has 1 month free subscription. Also, Watson by default has very limited translation languages pairs available. You can find out which pairs are available as described here If pair is not available you will encounter error message "model not found". In this case, you will need to create your own model as described here here. For us it looks as super overcomplicated procedure, so we did not try or test it.
- Go to Configuration->Locale and add field of type string, named "watsonLanguage"
- Sign up for IBM translation service as described here here
- Get your user/password pair as described here
- Go to Settings->Translation and fill in your user and password
- Go to Database->Localization and for each locale fill "watsonLanguage" field with the right language
- Choose any table with "localization" (Locale) or "localizationSingleValue" (Locale-S) types and string/text field type. Click on Setup and choose Watson as translation service. Choose your source language and destination languages.
- Click "Run" to translate several rows. Click T↑ to translate one row to all locales. Click T↓ to translate current row to one locale