I just got my B3 a few days ago, and here is how I got it to work in Garage Band (haven't tried Sequel LE yet):
1. Went to System Properties -> Sound and made sure Zoom showed up under "Input".
1. Create a new project. (File -> New). I just chose "Empty Project", but others might work.
2. It should come up with dialog asking you whether you want a software instrument or "Audio" or a "Drummer". If the dialog doesn't show up, either hit the little "+" button on the top left in the Track listing (which should be empty) or go to "Track -> New"
3. Select "Record using a microphone or Line instrument". Under input, I chose "Audio 1" and under that is said "My instrument is connected with "Zoom G Series"". Check the "I want to hear my instrument as I play and record" and it should list "I hear sound from "Built-In Output"" (I'm using a Macbook Pro, so if you have external speakers, this may be different".
4. Your new track should show up in the track list and you should be able to play and hear yourself. Note that some of the patches appear to be a lot quieter than others, so you might want to cycle through a few if you don't hear anything right-away.
HTH