Custom field translation

Hi, unfortunately I have not found a helping answer on this question.

I have added a custom field to my posts with the “WP Subtitle” plugin.

Now I want to add the WP Globus localisation to this field. Currently WordPress treats the custom field as one in all languages. So if I change the field text in Spanish, it’s also changed in English.

How can I tell WPGlobus that a custom post field needs to be translated?

Thank you very much.