did you check the manual here: http://www.cgi-central.net/scripts/amember/docs/ I know it is frustrating to set it up, but the reality is that EVERYONE seems to have a different setup. It is almost impossible to serve everyone's needs in a manual. It is good software, with quirks.
You know... I found that one of the best resources for aMember set up is at www.membershipacademy.com . The membership fee is very reasonable , and you get tons of step-by-step aMember videos that are extremely informative. David also has videos on all kinds of hacks or modifications that you can do on aMember, which really customizes aMember to fit your needs. His videos go also go through integration processes using systems like Joomla, Wordpress, phpbb, paypal, clickbank, etc.