Open the Tax Classes tab on the Taxes page of your X-Cart Admin area:

Click the New tax class button (Add New Class in X-Cart 5.5.x). You will see a blank field below.

You add as many fields as you need.

Use the field you have added to enter the name of a new tax class (e.g., "Alcohol" on the sample) and Save changes:

That's all. A tax class has been created.