Select an Instrument Channel Strip (on the righthand side), and the Software Instrument Channel Strip Inspector will show up at the bottom of the Edit window.
In the Channel Strip Library, scroll down and select GarageBand:
Swirling Droplets is under Synth Pads, Space Harpsichord is under Synth Basics
MacPro 2x2.26 Quad 28Gb OSX.10.7.5, OSX 10.8.3 Pro 9.1.8
MacBook Pro Quad 2.6 16Gb OSX.10.8.3 Pro 9.1.8