1. To get a IBM Watson Translator API key, you need to sign up for IBM cloud account at here:- https://cloud.ibm.com/registration
ibm-cloud-registration

2. After sign up, visit:- https://cloud.ibm.com/catalog and search translate inside top search box.

ibm-watson-translator

3. Now select free plan and activate translator service.

ibm-watson-translator-api

4. Now visit resources tab – https://cloud.ibm.com/resources and select translator service activated in last step.

ibm-translator-api

5. Copy the API key & API URL and enter both inside plugin settings.

ibm-translate-api-key