乗る and 降りる: particles for getting on and off
Contrast moving onto a vehicle with moving out of it. Learn vehicle に with 乗る, vehicle を with 降りる, and place で for the boarding or alighting point.
乗る: mark the vehicle with に
乗る describes boarding or getting onto a bus, train, bicycle, or other vehicle. 毎朝、電車に乗ります。 marks the vehicle being boarded or mounted with に; 電車を乗ります is not the basic pattern.
新宿駅で電車に乗りました。 uses 新宿駅で for the place where boarding occurred and 電車に for the vehicle. Keep place and vehicle separate instead of saying 駅に乗る as if the station were boarded.
降りる: mark the vehicle with を
降りる describes getting out of a vehicle. 東京駅で新幹線を降ります。 Here, 新幹線を is the vehicle being left, while 東京駅で is the place where the person gets off.
から can emphasize the starting point, as in バスから降りました。 In the basic vehicle plus を pattern, を does not mean that the rider acts on the vehicle; with this movement verb, it marks what the person leaves.
Being aboard and choosing an alighting point
今、電車に乗っています。 can describe the current state of being aboard a train. 電車に乗ります。 can instead refer to an upcoming trip or a habitual choice, so read tense and context together.
次の駅で降ります。 The vehicle is understood from context, and で identifies the alighting point. Do not mechanically replace it with 次の駅に降ります merely because the station is a destination in the wider journey.
Quick check: Which particles complete 京都駅（ ）バス（ ）降りました to mean “I got off the bus at Kyoto Station”?
Show the answer and why
Use 京都駅でバスを降りました。 The place where alighting occurs takes で, and the vehicle being left takes を.