Initially you can craft only gear to your own race style. You will learn other styles from racial motif books. You will find them occasionally when looting containers like backpacks, nightstands etc. You can also buy them from guild vendors with few hundred gold. Read the book and you have permanently learned that style.

All of the above comments are correct but keep in mind that these styles are not account bound... they are character bound. For clarification: if you learn a style on the first toon you make and decide to delete it you no longer have access to that style on other toons until you acquire the motif and learn it in the same fashion as you did on your first toon.

The only thing I don't know for sure is if this applies to the Crown store purchases. These might be unlocked for all your toons but haven't bought any personally so I can't say. If anyone knows more about the Crown store motifs your knowledge in this would be much appreciated.