There are two negatives and they mean the same thing. Put 안 directly before the verb - 안 먹어요 - or attach -지 않아요 to the stem: 먹지 않아요. The short form is more common in speech, the long one slightly more formal.
Examples
- 저는 커피를 안 마셔요.
- I don't drink coffee.
- 고기를 먹지 않아요.
- I don't eat meat.
- 오늘은 안 바빠요.
- I'm not busy today.
The mistake to avoid
With 하다 verbs the 안 goes inside: 공부 안 해요, not "안 공부해요".
Where this fits in
음식과 주문, Korean A1: Order in a café, ask for things politely, talk about favorite foods, and ask for the bill.