Let's say you wanted to show the WooCommerce cart in a sidebar but only on the about page. You would add the WooCommerce cart to your sidebar and then at the bottom of the widget under the 'Widget Logic' header you would add something like:

is_page('about')

So, only display where the page name is about.

or lets say you wanted to show another widget but only on the home page, you would add the widget to your sidebar and then add the following under the 'widget logic' header.

is_front_page()

This uses built in WordPress Logic. You can see a full list of them here:

http://codex.wordpress.org/Conditional_Tags

and some examples on the Widget Logic plugin page here:

https://wordpress.org/plugins/widget-logic/other_notes/