Dialing in your magnetic system is easy.
First start with the cast control knob on the handle side of your reel. With your lure attached and thumb-bar depressed, slowly back the cast control knob off until your bait falls slowly.
Now adjust your magnetic control 1/2 - 2/3 of its maximum setting.
Make your casts smooth and easy with your thumb just over your spool. You probably won't get geat distance, but as you get more comfortable with casting, you'll back both the cast-control and magnetic adjustment and your accuracy and distance will come.
It takes some time, but is well worth it.
This might help:
http://www.bassresource.com/bass-fishing-forums/topic/172271-how-to-cast-a-baitcaster/