In wp-admin, go to Plugins, then Add New, and search for DiscountWise. Or upload the plugin zip under Plugins, Add New, Upload Plugin.
Click Activate. WooCommerce must be installed and active first, since DiscountWise works on your WooCommerce prices.
A new DiscountWise menu appears in the wp-admin sidebar. It has four screens: Rules, Add New, Templates, and Why this price?