The taxes you've created should automatically apply to the current sale. You can turn a tax on or off during checkout by tapping the tax and adjusting the toggle next to "Enabled."
When you enable a new tax, it'll apply to all items by default as well. If you'd like to apply a tax to specific items only; head to your Items in your online dashboard, select an item, and check the box next to the tax you’d like to enable.
More info on managing your Taxes here: https://squareup.com/help/article/5061
I'll also point you to our Support Center for creating and adding discounts too! More info here: https://squareup.com/help/us/en/article/3955-create-and-manage-discounts
Hope that helps!
