add a second power supply

Suffice to say this dumb question is at my own risk, so here goes...

Have an Acer relatively new and great machine, but graphics are a little underpowered.  Bought a card and attempted an install only to find the power supply is a bit proprietary.  The power runs through the mother board to peripherals and doesn't have excess supply for graphics card.

In the face of this odd duck, here is question:  Bought a second power supply before I realized the on board supply was so proprietary.  How can I power the card with second power supply, external to the pc chassis?  

I attempted this (yes, as I stated; this is at my own risk) but the power supply didn't turn on.  Am assuming that it is looking for a signal from the mother board but it's not connected to one.  So I can get power to card using 2nd supply, but need to know how to trigger second supply to power up?

2nd power supply is a Cooler Master GXII 650 watt.
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Here's how to turn on a power supply without being connected to the computer. Don't electrocute yourself:

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VirtualKansasAuthor Commented:
Yep; I figured it was a paper clip trick.
A power supply tester will accomplish the same thing without needing to have  paperclips hanging out of the 24-pin connector.
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