Shouldn't the English translation listed be "We [sit] on the bench that's furthest away." Instead of "We [are sitting] on the bench that is furthest away.
I understand that you are asking for the El Presente conjugation of sentarse in this question. I originally answered it as something like "estamos sentiando" because I saw [are sitting].
Because in another question a few below goes like "Ella [esta comiendo] en el restaurante." I understand this one is asking for Presente Progresivo/Continuo.