Go to Appearance > Widgets in the main menu
On the right side of this page you will see the available widget areas.If you have not imported the demo content you will see 1 widget areas created when you install the Ella theme: the Default sidebar widget area.
These widget areas will be empty and so will appear minimized.
Widgets, once added to the sidebar will expand so that you can fill in the various options associated with that specific widget.
Once you have completed the widget options, click Save and then "close" to minimize the widget.