。
You absolutely have to turn in the homework by Thursday.
Literal
Thursday [by-までに-は] without-fail homework [object-を] submit must [emphatic-よ].
までには is the deadline marker までに ('by') with topic-contrast は added — 'by Thursday at the latest, in any case.' 必ず ('without fail') reinforces the absoluteness. ~しなければなりません is the polite obligation form, literally 'if you don't do, it will not become' — Japanese expresses 'must' through a conditional + 'is not OK.' Final よ marks the statement as new, important info.