phpMyAdmin is the GUI frontend to mySQL so do your editing in there.
Go to:
http://localhost/xampp/index.php
Look for
phpMyAdmin under
Tools in the left hand menu and click on it.
If you have set a mySQL root user password you will be presented with a login screen.
At the top left hand side of this screen you will see a Language drop box.
Select the language you want to use.
Now enter your root username and password in the boxes provided.
When inside phpMySql you can change the
MySQL connection collation to
gbk and you can do the same for any database on an individual basis.
Click on
phpMyAdmin documentation which may give more info on collation.
The phpMyAdmin web site is:
http://www.phpmyadmin.net/home_page/index.php