You can use the system's scode for upselling or for setting up item specific discount coupons in Mal's but you need to first know the scode for the item.
Find the product ID for the item that will be discounted. This is found in the link. For instance, a link:
and a link:
both refer to the product with an ID of 34.
In Mals, select the 'Discount coupons' from the 'Discounts' tab under 'Cart setup'.
Under "The discount is applied if the order contains a product with an SKU (scode)...", select "Begins with *", and then enter the product ID (from step 5) - along with a dash - into the SKU (scode) field.
ie.) In the above example, you would add "34-" (without the quotes).
Add the rest of the coupon as desired.