As far as I know, you can’t. WordPress comes with a bunch of widgets on the left hand side of the “dashborad/appearance/widgets” screen. You can add those to the right hand side of the screen and make the widgets appear in your theme. You will most likely find the same items that were originally on your sidebar in this list of “factory installed” widgets. One of the benefits of using widgets is that you can modify most ( if not all of your sidebar ) from the wp-admin without having to touch a bit of html-css-php.