English is the default language for WordPress. You can install or translate WordPress in other supported languages.
Suppose if you have missed language selection step during installation, you can change the language from English to another language using WP_LANG option on wp-config.php file.
Translate WordPress into other language
1. Goto below link to see all available languages supported by WordPress
WordPress in your language
2. Open wp-config.php file via FTP
3. Find your required language and copy corresponding WP Locale (third column)
4. For example, if you want to translate WordPress to French, then WP Locale is fr_FR
4. Now add/replace the below line BEFORE /* That’s all, stop editing! Happy blogging. */ in wp-config.php
define ('WPLANG', ' ');
define ('WPLANG', 'fr_FR');
5. Save the file and upload it to the root directory via FTP. Confirm rewrite/replace the file if any confirmation popups.
6. Now, open your WordPress site and you will see it in French language.