Translation to languages

Hi. Thanks for the nice plugin!
Can you please make some instructions on how to translate it to other languages?
I’m using icon captcha and via settings, I can change only “Captcha Title”, “Captcha Empty Messages” and “Captcha Error Messages”. However, I did not found how to change the description of the icon user should select i.e. “Soft Drinks”, “Flag”, “Paint”, “Car” etc.
Using Loco Translate plugin I generated wp-captcha.pot file but unfortunately, those names (“Flag”, “Paint”, “Car”) are not included there.
Any advice appriciated.