To get started with translations go to https://www.facebook.com/translations.
Select the language you are going to translate into. Note that once you set a
language you can only change to another language after 30 days. Please also
change the language you are using Facebook in to the language you are
translating into. This will enable you to see your translations in context to
check their accuracy. If there’s a mismatch between those settings you will see
the following message in the translation app: