Best place to start is the Ross Tech Wiki pages. They also have a forum for registered users. VCDS is very user friendly and generally won't let you do anything major without prompting you.
The checking for fault codes (scan) is easy as you just click on 'Auto Scan' and it will scan every module in the car. Any faults will show in red and you can then click on them to see what the code is. If you want to just interrogate one module, you can select it manually.
http://wiki.ross-tech.com/wiki/index.php/Main_Page