HELP! I Do Not Understand this FitBit Thing!

So I purchased a Fitbit thinking it would help me be a little more accurate with my excersise. I am not the most savvy gadget-girl, but I did manage to sync the fitbit with MFP account successfully. I was under the impression that this FitBit synched itself automatically to my computer when I came home for the day. However, it is not doing this. Calories burned on the Fitbit does not match that on MFP at all! Can anyone tell me what they do to ensure that their info is tracked accurately...or at all! Thanks guys!!!