Turn on Tx
Hold down calibration button on esc power switch and switch on esc. Esc will start beeping.
Let go of calibration button
Hold full throttle then press and release calibration button. You will hear two beeps.
Hold full reverse then press and release calibration button. You will hear three beeps.
Now switch off esc. Calibration is complete. With Tx still on, switch on esc and test forward and reverse.

This procedure must be done after you change parameters in the esc through your computer.