FitBit: tracking your exercise...?

I have a question for all you savvy FitBit users. I just bought mine yesterday, and today was my first full day wearing it. I did a workout DVD (in addition to my normal walking for the day), and the FitBit integrated with MFP for a projected amount of calories burned...does that mean I don't need to log my exercise in MFP or do I do it in conjunction with what the FitBit picks up on? I'm using the Flex if that matters at all.