a couple tips:
Yes, you do need a registration number and a password. You enter these in the according fields of the connection window. Registration number and password have been issued to you when you registered with Vatsim. Your number is 904030, but I donÂ´t know your password...
Your serverlist may be outdated. In your squawkbox directory you will find a file called "ipaddr.txt". Open this file with any text editor and replace its content with the following:
This is the most recent server list available as of today. Once you have put that list into your ipaddr.txt-file, save it, return to the flight simulator and try to connect again. You should be able to select among these servers now, and depending on your (real, not sim) location you should pick the one closest to you.
You can update this serverlist yourself in the future by using ServInfo (which is recommended regardless of this, itÂ´s a very nice tool). Just click on "File" -> "Export ipaddr.txt", select your Squawkbox directory and click "Save".
In the connection window, make sure to check the box where it says "Use Roger Wilco voice", even though you are using AVC (this is a leftover from the time when Squawkbox 2.3 was developed. AVC didnÂ´t exist yet back then). Leave the field with the voice server address empty (AVC will fetch the appropriate server itself once you connect to a controller). This way you wonÂ´t get that infamous "You must be connected to a Vatsim server first" message.
The above points should sort out your problems. Unfortunately you sort of picked a bad time for getting started...
Squawkbox 2.3 is everything but user friendly and connecting with it for the first time can be a real pain in the a$$ for people not used to it. Fortunately however, Squawkbox 3, written by Joel DeYoung, has been under development for some time now and is due to be released somewhere around the end of March. Squawkbox 3 will be very user friendly and intuitive.