Steps

1. Go to the Apps section of your Shopify store, and click on the Auto Multi-Channel Fulfillment app
   
2. Open the Configuration Page > Shopify Setting
   
3. Scroll down to the Show All Amazon shipping speeds to Customer (Amazon's Real-time shipping rates) setting
   
4. Click on the Add Markup button to see the below-displayed options
   
   
5. The primary Amazon fulfillment methods are Standard, Expedited, and Priority.
   
   
   1. Show on Website: If you turn on this toggle, then we will start showing the selected shipping method along with its defined values during an order checkout.
      
   2. Override: If you want to give a custom name to any shipping method, just check the Override box, further enter its name in the name box, and hit the Save button.
      
   3. Shipping Cost Markup: This can be done by either a Flat Fee OR a Percentage of the total shipping fee. For example: If Amazon's standard shipping rate is $5.00, and you added a $5 flat markup, then during checkout, $10 will be the total shipping cost that will be displayed to the customer. 
      
      Note: If you want to offer discounted shipping, then enter a negative value. For example, $5 (flat fee) OR -5% (percentage fee).
      
      
   4. Free over (Order total): If you want to offer a free shipping cost, above a certain order value, just enter the amount in this field, and hit the Save button.
      
      Note: Make sure to hit the "Save" button, after modifying anything in this Add Markup option.