Some stores may want to have different default locales for each of their sites in a MultiStore instance. For example, a US store wanting to expand sales into France can go to the effort of setting up a new store with a .fr domain, but customers are going to be most comfortable shopping on a site in their native language. Any locales published on the site will be available to customers to choose from on the front-end (provided your skin template allows this), but it would be preferable to default each site to the native language that most of its visitors will use.
While the basics of installing multiple locales are simple, there are some extra steps to take for MultiStore sites. Please see this page for information on basic localization tasks if there are questions on any steps in this guide.
Setup
1 - First, make sure that the currencies that you want to support have all been created.
2 - Next, add the locales that you are going to support.
3 - Finally, set the DefaultLocale AppConfig as desired for each of your stores. See this page for information on setting store-specific AppConfigs.
That's it! New visitors to your sites will see the locale set for the store they hit. Remember that the chosen locale is saved on customer records and in session data (Profile table in database), so if you've already visited a site and then later change its default locale, you may have to clear your browser cache & cookies, or even manually choose the new locale before it will appear to you. Testing in a different browser as an anonymous customer will allow you to see what new customers will see.
A note on currencies
While the software supports having multiple currencies enabled, with customers able to choose what currency to view the site in (provided your skin allows this), the default currency cannot currently be set per store. The first currency customers see will be the same across all of your sites.
Note that you can change which currency is used when transactions are sent to the gateway for each "MoreStore" site by setting store-specific values in the Localization.StoreCurrency and Localization.StoreCurrencyNumericCode AppConfigs, but it is not generally recommended to do this. Since product price cannot currently vary by store, it is best to stick with one currency, or at most use additional currencies for display purposes only. Doing more than that can lead to confusion in what the base price of a product is, and what will really be sent to the gateway and show up on the customers' receipts.