# Download the .mo file for your language. As you probably noticed the naming convention of the .mo files is based on the ISO-639 language code (e.g. pt for Portuguese) followed by the ISO-3166 country code (e.g. _PT for Portugal or _BR for Brazil). So if you see more language files for your language, select the one specific for your country.
# Open your config.php file in a text editor (remember: never use word processors like MS Word for editing the files!) and find this around line 15: define ('WPLANG', '');
Edit this line according to the .mo file you’ve just downloaded, e.g. for the Portuguese spoken in Brazil you must add: define ('WPLANG', 'pt_BR');
Save it.
# Go to your installed WordPress (i.e. your server or your hosted account) and create a directory (folder) in your /wp-includes directory and name it /languages. Upload the .mo file there.
# Don’t forget to upload the modified config.php file into the WordPress root directory.
# Open your browser and go to your WordPress URI (address). It should display in the newly installed language.
# Additionally you can download the .po file and customize/personalize the translation, but at the end you need to save it and create a new .mo file.
Note. If there was an error in the steps above or you did not specified the correct langauge WordPress will default back to English.
