This plugin is delivered with the NopAdvance Core plugin on which this plugin is dependent. You need to install the plugin using the plugin installation guide provided here.

Once the plugin has been installed, you will see the plugin menu under NopAdvance > Plugins > Product Offers in your nopCommerce admin menu, similar as displayed in the below image.

Click on the Configure menu item from the Product Offers menu as displayed above and you will be redirected to the plugin Configuration page.