1. Download the language pack you need and then unpack it to your Magento install folder. It copies two folders: one goes to appdesignfrontenddefaultdefaultlocale and the other one to applocale.
2. Go to System > Configuration in your admin. On the left top corner in Current Configuration Scope dropdown box, you can see Default Config, and Main Store in English store view.
3. Now let’s go and add the French store view. Under the dropdown box, there’s Manage Stores link or you can directly go to System > Manage Stores. Click the Create Store View link on top right, and type these in store view information form: Store: Main Store Name: French Code: french Status: Enabled Sort order: 0
4. Save, go back to System > Configuration. In Current Configuration Scope dropdown box, you now see there’s French store view. Click that link. On Locale options tab on the left, uncheck the “use website” checkbox then change the locale to French (France). Save. Now you can have your website in French.