Unless i have misunderstood you, and that the board powers a couple of slots off of the atx connector, you just plug in cables from your server psu. You dont use the pico to power any pcie. Infact it doesnt have a pcie output. The one in the pic is for 12v input - not an output.
My fault no yours that you don't understand odna boards.
they have six inputs for the six slots on the board.
3 are molex and 3 are sata
you need to feed those inputs with sata and molex cables
https://www.youtube.com/watch?v=TMiByCbUpTY&t=15sgo to about 1:35