ln -s /usr/GuineaPig/demos/demo/* .
(there is a space between the asterisk and the dot). This will make symbolic links to the demo files in your directory.
./testAB.properties
or
gpRunTest -f testAB.properties
to run the A/B test example. You can also run gpRunTest without config file name as argument. If so, a dialog is shown to select config file. For the 'session type', select 'single subject' for now. The testAB.properties is a test configuration file name. Also look at the manual about running a test.