How to us it?

1. Installation

At first make sure you have the latest ecommerce package before installation. There was a bug on earlier version which doesn't install the discounttype correctly. See more here. The package installation occurs as a normal concrete5 add-on installation. You can purchase the package directly from your dashboard or purchase it on the marketplace and upload it to the packages folder via FTP, and then install the package from the dashboard installation page.

2. Using it

Discount type enables the discount type automatically during the installation. You can then find the discount type in the adding discount list. (Url: /dashboard/core_commerce/discounts/) 

Choose the "tiered discount"-type in the dropdown list and hit go. Remember that by default the discount code status is disabled so if you want to enable it right away you need to change the status to enabled. And on the bottom there is the adjustment.

Applies to gives you to choose wheter it is for all products, specific product(s) or specific product set(s). Second one "Based on" is the what will be used while calculating the discount either price or quantity which is the total of matched products by applies to selection. Type is the discount type either amount or percent. And the last is for the tier list. "From" means the Based on value giving followed by "Discount" amount or percent discount from all matched products price.