NO. (this will be done automatically) but you want to crop/extract the rectangular region around your object using the annotation tool, and pass an info.txt file with those boxes to the createsamples tool.
this is a bit tricky. the size there is the minimum size, that can be detected later, so on the one hand, this should be as small as possible, on the other hand, a larger one might give you a better detection. e.g. the face-cascades were trained using a 24x24 rect. also note, that memory usage during the training goes exponentially with the size there, so keep it as low as possible.
