The PSU I have has one 6 pin but the card needs 2 6 pin what do I do then?
looking at the OCZ Specs your PSU should have 2 PCI-E cables.
http://www.ocztechnology.com/ocz-zs-series-550w-750w-power-supply.html
Edit: The ZS Series was launched in 2011 and you should have 1 x 6 pin & 1 x 6 + 2 pin connections so the adapter should not be needed.