With Blissful Blog, you have to go to appearance > widgets in the dashboard and add in the widgets that you want in your sidebar and then they will appear on the page. If you have not yet added any widgets at appearance > widgets, then the theme defaults to one column.
Blissful Blog offers a sidebar template on single page, archive, and search views, and three footer widget areas on any page. You can assign widgets to each of these areas by going to Appearance -> Widgets. http://theme.wordpress.com/themes/blissful-blog/