Arduino Mega2560 Manual page 11

Caution:
When insert/remove the 6-pin parallel cable plug into Model X 6-pin male
socket, please hold the black plastic pin-holder to do operation. Never drag the
wires to pull the plug out of the socket, otherwise it will damage the wires.
Picture 13: Connect Model X board (L298N) to front motors
Picture 14: connect another model X board(L298N) to rear motors.
Picture 15: Connect Front Model X pins to MEGA2560