you cant unless you buy someone elses starter wolf (the two wolves you start with are called starters, also known as 'lone wolves'

You can also create a new wolf (with lone wolf bloodlines) in the Custom Maker.

These wolves are known as generation one wolves, or G1 wolves. If you type in sire number or dam number as "0" in realm > trading post and look for some for sale, you should guaranteed find some.