As of firmware version 1.50a, you can control the send level of the FX channels to the Auxes by using Aux Flip Mode. To enter Aux Flip Mode, select the Aux channel that you want to use, then double tap the Mix button. This will switch the first 6 meters and encoders to become the Aux-send level controls for the following:
When you are in Aux Flip Mode, the Mix button will remain illuminated and the LEDs at the top, middle, and bottom of meters 7-16 will also illuminate. Turn the Fat Channel encoders for FX A or FX B to adjust the level being sent to the selected Aux.
For more information, see page 45 in your StudioLive manual.
If you are on a firmware version lower than 1.50a, go to page 4 of the FX menu of the Studio Live. There, you can directly patch FX A/B to the desired Aux output.