How do I select another Map Theme as default when starting a new mindmap

I use Mindjet 14 for Windows. I do not want to use the default style, but the classic one. How do I select another Map theme as default when I start a new blank mindmap. To find the answer: I Googled, used the mindmanager help-pages and searched this community, but did not find the answer. It is probably very easy, but I cannot figure it out. Thank in advance for your answer.