How do I offer free shipping as a coupon benefit?

Use the Free Shipping discount type to waive shipping charges when a coupon or automatic discount is applied.

Go to Marketing and then Coupons and click + New.
Enter a name and a coupon code, or click Generate Code.
Under Apply As, choose Coupon so customers enter the code, or Automatic Discount to apply it at checkout without a code.
Under Discount Details, set Discount Type to Free Shipping. No discount value is needed.
Optional: Under Restrict Coupon Based On, enable Set Minimum Cart Amount to offer free shipping only above a threshold, or add other restrictions such as eligible shipping zones or customers.
Set the Offer Period (Valid From and Valid Till, or Never Expires) and any Usage Limitation (Online Store Limit, Customer Limit).
Turn on Show in Online Store to display the coupon on your store’s checkout page.
Turn on Active Coupon and click Save.