Start with this...
http://www.subsim.com/radioroom/showthread.php?t=128185
The download this
http://www.subsim.com/radioroom/showthread.php?t=111445
Then read this...
http://www.subsim.com/radioroom/showthread.php?t=111509
Once you are comfortable with the above have a look here. Tons of useful, valuable information here...
http://www.subsim.com/radioroom/showthread.php?t=108931
And last, but not least, once you have specific questions come here to ask them. Lots of people here will be glad to help.
JCC