How to rename WP through phpMyAdmin

You can see the official wordpress how-to for changing the url here:

http://codex.wordpress.org/Changing_The_Site_URL

or if you want to change it through the database see the following guide  HERE

 How to log in the backend of WordPress

Once logged in you will go to Settings -> General

You will see the current site url, you can update it to the new one

and SAVE IT!