[Cerrado] Theme level translations via code

I'd like to translate certain text at the theme level such as 'Related Issues' and 'Related Content' on a page like enlace oculto. I followed enlace oculto
but interested to do this via code because I have numerous sites using the same theme. Could you provide details on how this can be accomplished? I looked into this thread https://wordpress.stackexchange.com/questions/127917/generating-po-mo-translating-files-from-scratch-in-a-wordpress-theme/320250#320250 but not sure if I should follow this approach.

Thanks