Using this rule you can give a discount on the least amount product in the cart, you can also set it to free.
For making this discount rule select Discount Rules tab.
Now choose the Least Amount Product Free Rule
Now click on Add New Rule.
Activate this rule by enabling Rule Permission.
Add restriction on this discount rule by clicking on the restriction tab as shown below
Enter rule start and end date in the validity section.
After entering these dates click on the Save Rule button.
Now your rule is active.