The Polygon Documentation
The theme suggests the installation of three plugins: YITH Essential Kit for WooCommerce#1, YITH WooCommerce Added to Cart Popup and YITH WooCommerce Social Login. Once installed, you can find them in the YIT Plugins section of the theme.
The installation of YITH Essential Kit for WooCommerce #1 lets you use the free version of many plugins, allowing you to benefit from different features for your site. Each single plugin can be activated or deactivated directly from the panel.
In order to change the settings of the activated plugins, you just need to select the one you want from the list you can find in YIT plugins. For further information about how plugins work and how to configure them, please read the correlated documentation in this page.
On the contrary, you can activate the YITH WooCommerce Added to Cart Popup and YITH WooCommerce Social Login plugins. Once installed, go to the Appearance -> Install Plugins section to activate them.