Hello, You do not have to modify de code. The theme already have a folder named “languages”, you just have to copy the files inside.
In the theme folder you will find the original languages files “en_US.mo” and “en_US.po”. When you copy these new files “es_ES”, you will add this translation to the theme. (you can modify or create your own translations with the app poedit)
BUT, VERY IMPORTANT, you have to configure wordpress in spanish. If you don’t do it, the site will not recognize this language.
This link explains how you can do it:
https://webconwordpress.wordpress.com/2011/04/06/cambiar-idioma-y-plantilla-al-configurar-wordpress/
Another link:
Home