Google Cloud Translator offers a free tier of 500k of translated chars each month. More pricing information here.
To be able to translate contents with Google, you need a Google Cloud Platform account with billing enabled and a service account key. You can create an account and a service account key following Google official instruction.
Make sure to download and keep the service account key in a safe place.
Click on the Google Cloud translator pencil;
Upload your Google Cloud Service account key and click Save.
Once saved, the key will be encrypted and you will no longer be able to see it. Keep a copy of your service account key in a safe place.
Lango will verify your configuration. If everything goes well, the provider will be set as active and default, as in the screen below.
If you see this screen, something goes wrong.
You have uploaded an invalid service account key. Make sure that the file you have uploaded is the same that you have downloaded from Google Cloud;
You don’t have activated the Google Cloud Translator API on your Google Account;
Your service account doesn’t have the right permissions to access the Cloud Translator API. Check the service account permission on the IAM settings;
You don’t have the billing active on your Google Account. Make sure you have a valid payment method;