To use the Easy U.S. Sales Tax add-on, you'll need to create an account with TaxCloud.
You'll install the Easy U.S. Sales Tax add-on as you would any other plugin. Then go into Exchange > Add-ons and click the gear symbol to the left of the Enabled button for Easy U.S. Sales Tax.
The first group of settings you'll find there will be for your TaxCloud API IDs and Keys.
Next you'll enter your business's primary address.
Lastly, you'll go into the General Settings. You can opt to enable Tax Exemptions for qualified customers.