This video explains how to create promotion on Amazon seller central using manage promotions tab.

This Tool Automatically Tracks Amazon Seller Coupons. Setup Email Alerts and Automatically Hold Inventory for Coupon Promotions Setup by an Amazon Seller. No Longer do you have to worry about a customer posting your Coupons onto a Deal Site when you don’t want them too. This Tool Automatically Alerts you when the Coupon you are promoting has been used up. ...