Add a Free Shipping Method

Access: E-commerce>Configuration>Shipping.

Click the Price Rules tab. (If this tab is not available, check the Price-Based Shipping box above, then select the Submit button.)

Select Add New Shipping Method.
Enter a Name for your shipping method (ex. Free Shipping).
(Optional) Description details the shipping method and will display in the shipping options section of the checkout process. (ex. "Orders $100 & over qualify for Free Shipping!".)
The Free Display is 'pricing' text which also displays in the shipping options section of the checkout process. This should say "Free" or "Free Shipping".
Click Save & Edit.
On the Rules tab, select Add New Rule.
For the Start Cart Price, enter the minimum sub-total amount (pre-tax) a customer must spend in order to qualify for free shipping. (i.e. if you want orders $100 and over to be free shipping, enter "100".)
Is Available? needs to be set to Yes, and Price set to "0".
Click Save.
The first rule that appears in your list should say $ 0.00 - $ *your start cart price*. Click the 'Edit' icon and change Is Available? to NO.
Save the rule, then Save the shipping method editor.

(ex., if your free shipping requires a $100 minimum purchase, sub-totals (pre-tax) of $99.99 and below will NOT qualify (nor display as an option), but $100.00 and up will.)

Be sure to run-through the checkout process to test the free shipping. First, add a product to your cart BELOW the minimum spend amount, then proceed through the checkout process to see the shipping methods screen. The method should NOT be available. Next, up the quantity in your cart to reach AT, or go ABOVE the minimum spend amount and proceed to the shipping methods screen. The method SHOULD be available.