Download Psychtoolbox here.
Type help PsychDemos in the command window to see Psychtoolbox's built-in demos
Dr. Peter Scarfe's tutorials are also helpful and have line-by-line comments. These are available here.
Dr. Kaplan teaches a Psychtoolbox course at USC, you can find his powerpoint slides on his page here. Or at our lab dropbox: here.
See this example of how to train your RA (including detailed breakdown of simple tasks.)