By placing a large catch tray underneath & undoing all the bolts on the transmission sump. Keep two end bolts on the same side for last as the pan will gradually tilt and let all the old fluid out. There would be roughly around 6-7 litres(guessing) of fluid. youo would normally have prepurchased a filter kit which should include a new filter and sump gasket. Make sure you clean the pan out well and also the magnet that sits in the bottom.
Wat if the ute ilmobizers it's self when u change the oil. How do u unilmobi do it? And get it started again?