"Do not give it food."
Translation:उसे खाना मत दो।
उसे - 'To it' (or alternatively 'to her', 'to him)
खाना- 'Food' (खाना is also the verb 'to eat'. Sort of like how 'cook' can be both a noun and a verb in English)
दो- Give (Imperative form of the verb देना-'to give' which is used for giving out commands and making requests)
So, उसे खाना दो = 'Give food to it' = 'Give it food'
मत introduces negation
उसे खाना मत दो = 'Don't give it food'