Translate website to another language
Currently the Essentials theme is available only in English, however, the theme is translation ready and you can translate it to other languages using a translation plugin (for example Loco translate), Loco translate plugin is used to translate the static strings of the website (for example: Read more, Comments, Search,… or any other word used in the theme or plugins), and you can translate these strings directly in Loco translate plugin into multiple languages.
For more information about translating your website to another language using Loco translate:
Translate website to multiple languages
If you want to make your website available in multiple languages at the same time, then you will need to install additional plugin (for example Polylang or WPML) to translate the content of your website into multiple languages (for example translate the content of the homepage, header, footer,…).
So if you want to have the website in English and French, you should install Loco translate plugin if you want to translate any static string into French, and you also need to install Polylang plugin (or WPML) then create a French version of each page you want to translate (you can duplicate the English version then change the text directly into the page builder).
You can add the language switcher to the header by editing it and add the language element via the header builder.