Sorry about the delay....here's how to do it
With the connector facing you and in an upright position (cables at the back, 2 rows of 10 sockets facing you) and the locking tab on the right hand side......short out the 2nd and 3rd down on the right.....they need to remain shorted for as long as you require the power supply to run.
ps. the 2 rows of ten might be 2 rows of 14 if the psu is from a larger server or new machine, but the above still applies