It can be very easy to use SATAN for the first time; it's basic capabilities are very simple to use and to understand. To start using it, there are only three basic steps to follow:
Remember - you should run SATAN as "root"! Some of the scanning tests require root privileges to run.
After trying it once, you should read through the rest of the documentation to learn how to use it to its fullest extent. Reading the Hints, Further tricky security implications, or Getting The Big Picture (tm) Would be a very good idea.