You don't. Mangia bene is Italian. In English you say "eat well."
Eat well is the literal English equivalent of 'Mangia bene'. A looser equivalent is 'Have a good meal' or 'Enjoy your food'. In the word by word translation, the imperative 'mangia' means '[you] eat'. The adverb 'bene' means 'well'.
I'll see you all on Tuesday.
Mangia happened in 2600.
Mangia was created in 1983.
John Mangia's birth name is John Michael Mangia.
Così fan tutti! in Italian means "All men do it!" or "Thus do they all!" in English.
Yes, 'enjoy' may be the English equivalent of 'mangia' in the sense of 'enjoy [your meal]'. The Italian word also may be translated as the wish to 'have a good meal'. It's the singular command form of the infinitive 'mangiare', which means 'to eat'.
"Tutti".
Mi piace! Grazie a tutti! in Italian means "I like (it)! Thanks to everybody!" in English.
mangia tanto (one people) mangiate tanto (more)
"Eat! Eat!" is a literal English equivalent of the Italian phrase Mangia! Mangia! The present imperative in the second person informal singular most correctly may be heard employed upon a listener who numbers among the speaker's close group of family, friends and peers even though it also may be used -- instead of the more correct, second person informal plural form Mangiate!([You all] eat!") -- with an intimate audience of more than one. The pronunciation will be "MAN-dja MAN-dja" in Italian.