What part has you confused?
If you look at the bridge rectifiers, one terminal is 90 degrees to the other 3.
Sometimes one corner is cut off.
The different one is positive.
This is pretty complete,
http://www.otherpower.com/rectifiers/schematic.JPGThe AC from the turbine goes into the AC terminals on the bridge, often marked AC or ~.
Positive output goes to the battery positive.
Negative output goes to the battery negative.
The bridge rectifiers they use in the example have both a cut corner and a 90 degree terminal indicating the positive terminal,
http://www.otherpower.com/images/may0106/my01_0018.jpgG-