This is not a template related question really, I'll answer shortly, please refer joomla.org for more questions "how Joomla works" and "how is default joomla installation".
Go to your admin panel, choose menu. Choose mainmenu and edit your Home link. There you have settings for the frontpage layout (as a default there is 2). How many columns you want to use? Go to the content -> frontpage menu. Choose the articles, you want to show on the frontpage (i.e. unpublish your Newsflash items) as a result, you will have only one article on the frontpage.
If you install Joomla with default content, the articles will have a certain places on your site. But because Joomla is a content management system, luckily, you can change this easily to meet your personal needs
