To change the language, you first have to enable the translator from Name -> Settings -> Company Settings -> Company Profile -> Language Translator and save the setting.
Once saved, you’ll spot the language switch dropdown menu at the very bottom of each page. Additionally, once enabled you can also choose the language during the account sign-in screen.
Note: the language change is algorithmic at the moment and may not be 100% accurate. It also does not affect any of the printouts (labels, invoices, etc)