In wp-admin, go to Plugins, then Add New, and search for Quotly. Or upload the plugin zip under Plugins, Add New, Upload Plugin.
Click Activate. WooCommerce must be active first, since Quotly quotes your WooCommerce products.
A Quotes menu appears in the sidebar with three screens: Quotes, Settings, and Add New.
On activation Quotly creates a page called Quote Basket holding the [quotly_basket] shortcode. You do not have to build it. It is already picked in Quotes, then Settings, then General.