changing language of WordPress

So I want to display various element that are called from WordPress, such as writting “search” in another language than English, by following WordPress codex instructions.

Here is what I did:
1. I added a languages folder to the wp-content folder (/wp-content/languages/)
2. I added fr_FR.mo files to that same languages folder (/wp-content/languages/)
3. I modified the wp-config.php file to include the line define(‘WPLANG’, ‘fr_FR’);
4. I also created a languages folder in the theme folder and put the .mo files there too… just in case

It worked somewhat however, everything that is being called by WP such as the ‘search function’, comments, etc is still in English.

Please help !!!

Thank you !