。
You really do need to quit smoking.
Literal
Truly cigarettes [object-を] quit-[must-なければいけない]-[insistence-よ].
~なければいけない is a compound 'must do' construction (lit. 'if one does not do X, it will not do'), near-synonymous with ~なければならない but slightly more colloquial and subjective. Sentence-final よ delivers it as urgent advice — 'you need to, I'm telling you.' タバコ, a 16th-century loanword from Portuguese tabaco, is one of the earliest European borrowings in Japanese and is conventionally written in katakana to mark its foreign origin.