auto show corresponding language when open website

[win8win]

such as my zencart website have already had two languages,English and Japanese,
if Japanese visited my website,they would see website in Japanese,
if others,see in English,

what should I do?

[DrByte]

Admin->Configuration->My Store->Language Selector

Language Selector
Should the default language be based on the Store preferences, or the customer's browser settings?

Default: Store's default settings

CHOICES:
-Default
-Browser

[win8win]

Thanks so much for DrByte,it works!