How can I format my blog in Mantra?

I’m using Mantra for my website which is so far just a main page with a shop which is not visible yet because I’m still working on it. I just imported my blog over from WordPress.com and I’d like to format it more like how it was over there. I need a sidebar with widgets. How can I do that? I chose the template to be blog for the page, where can I choose how the blog looks?