Where is "locales"

Hi!
Newbie here…

I want to change the language to french.
Red the instructions ==> Ghost Handlebars Theme Helpers: translate
I’ve created a folder on my computer called “locales”, created the fr.json and translated it.
How to I upload it / how do the site read it?

Thanks

The locales directory should be in the root directory of the theme you are using.
You can download it from Admin, add the locales folder inside the theme and re-upload it.
You have to set the language to fr in the Admin, going to Settings → General → Publication Language.