The examiner will ask you to pull up alongside a parked vehicle and reverse into a space behind it. You will have approximately two car lengths to work with. Success comes from careful positioning, steering at the right moment, and making small, controlled corrections.
Align your car with the parked vehicle, leaving about a metre of space. Your back bumper should be level with the back of the other car. Stop, select reverse, and check all around. Look over your left shoulder and begin reversing very slowly. When the back corner of the parked car lines up with your left rear window, steer one full turn to the left.
As your car swings inward, watch your right mirror. When the kerb appears at roughly a 45-degree angle in that mirror, steer two full turns to the right to straighten up. Continue reversing slowly until your car is parallel to the kerb, about 30cm away. Stop, apply the handbrake, and select neutral.
Because every car has different dimensions, the reference points that work for one vehicle may not work for another. Spend time with your instructor finding the markers that suit your test car. The examiner is judging control, observation, and reasonable accuracy: they are not expecting millimetre precision.