By default, the fields in the plugin settings screen are mapped to the relevant Woocommerce checkout fields. You shouldn’t need to do anything else; however, you may want to use the CSS options to customise the way the form looks.
The plugin only looks up UK addresses; if you ship to other countries (and therefore display the country selector dropdown on your checkout page), the postcode lookup will not show on the page after a country other than United Kingdom is selected.