を marks a place or a vehicle from which an action/movement begins. Typical verbs that are used with particle を with this meaning are でる(get out) and おりる(get off).
わたしは ぎんざ駅で 電車を おります。
I get off the train at Ginza Station.
わたしは 九時ごろ 家を でます。
I leave home at around 9 o'clock.