The instruction is very simple sink kwa rotate elbow and open without using force. I found that I could sink the kwa easily but then turned to force to open the grip.
Kelvin helped me first by holding my arms but then changed the grip to using a single finger against my arm instead of holding the arm. He indicated that I should warp around the finger. This helped, I found that after I sank by stretching my fingers and wrist open it allowed me to get a better movement in my elbow which in turn allowed me to better wrap around the finger.