"The chair is here, not the apple."
Translation:A szék van itt, nem az alma.
Because you are comparing "the chair" and "the apple" in being here or not, so "the chair" should come in front of the verb as that's the natural position of the focus.
Why does van come before itt? Why not itt before van? A szek itt van, nem az alma
Had you read back, you'd have seen the answer of mizinamo. Here it's very explicitly given what is the important new detail of the sentence - the chair is here, not the apple. So you'll have to focus the chair, ie it will precede the verb. And since here sounds like a "technical detail" (neither the topic discussed, nor the important detail, which was the chair), it is a natural idea to put it after the verb. :)