Your store can be configured to require that customers open an account before making a
purchase, or to allow unregistered guests to go through the checkout process.
To allow guest checkout:
1. On the Admin menu, select System > Configuration.
2. In the panel on the left under Sales, select Checkout.
3. Click to expand the Checkout Options section.
4. Set Allow Guest Checkout to “Yes.”
5. Click the Save Config button.