。
Hey, do your homework before dinner.
Literal
Dinner-before [at-に] homework [object-を] do-[imperative-しなさい]-[sentence-final-よ].
A pared-down, impatient instruction. しなさい is the soft imperative form built from する's masu-stem + なさい, used by parents to children, teachers to students, or instructions; the よ at the end adds urgency or exasperation. The speaker is probably a parent reminding a child who's been putting it off.