If I use an exercise device do I need to enter my exercise separately?

I just figured out how to sync my Misfit Flash to the MFP app. I have been using the Flash for about 6 months and know that it doesn't accurately track some types of exercise, such as yoga and Barre, that are not as vigorous as running but still use up a lot of calories.

So my question is this: how do I correctly capture all of the exercise I am doing, does the Misfit sync replace some or all of the data? An I really doubling up on my reported exercise when I also enter walking times?