When you start a serie of blogs you first choose Create new series.
I don't know whether you enter a blog series title for part two or whether you can still include part 1 under that. Try it I would say. ++++++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
