Configure this before you start selling, not after.
ENABLING TAX
WooCommerce > Settings > General, tick Enable tax rates and calculations. A Tax tab then appears in settings.
THE KEY DECISION
Whether your entered prices include tax or exclude it. Changing this later means reviewing every price in the catalogue.
For most consumer shops in Nigeria, entering prices inclusive of tax is simpler, because customers expect to see the price they pay.
SETTING RATES
WooCommerce > Settings > Tax > Standard rates. Add a row with the country, the rate, and a name.
Reduced and zero rate classes exist for products taxed differently. Assign products to a tax class on their General tab.
DISPLAY
Set whether prices show including or excluding tax in the shop and in the cart. Be consistent between the two, or customers see the price change at checkout and abandon.
GETTING IT RIGHT
Tax treatment depends on your business and your obligations. Speak to your accountant about what applies. We can tell you how to configure WooCommerce; what rate applies is not ours to advise on.