It involves a smooth transition from pedalling to walking along while pushing your bike. Take your left foot off the pedal and wait for the right pedal to reach the bottom of the stroke. As the pedal rises, straighten your right leg and let go of the bars; your bike should keep going forward, you should be able to put your left foot on the ground, grab the saddle and remove your right foot from the pedal. Significantly easer when not clipped in.