You can configure your business details by clicking Configuration in the shop management panel menu and then clicking Business details.
There are two settings in this section:
This is your shop name, as shown to customers in e-mails generated by the shop.
This is the default country for your shop. Tax rates vary between countries, and when a visitor is logged in they are shown the prices for their country. If a visitor is not logged in then they are shown the prices for the default country.
These are your legal details: your registered company name and address, your company registration number, your country of registration, and your tax registration number (which is your VAT registration number if you are based in the European Union).