Remove cables to PSU and monitor, as well as the SLI bridge. Unscrew the screws from the PCIe bracket at its left. At this point hold the graphics card so it doesn't bend downwards and break its slot, since nothing will prevent it from doing so. Look for the lever at the right end of the PCIe slot, that looks similar to the ones on the RAM slots. Press down on it, and pull the thing out of the slot.
One by one; top one first, then bottom one.