From v2.3
No database changes are required. Backup your template files and your config file. Overwrite all the files. Edit the new config file as needed and upload your template files over the new ones.

From v2.2
Same as for v2.3

From v2.1
Backup your database, template files and config file. Overwrite all the files. Edit the new config file as needed and upload your template files over the new ones.

Run the following command on your database:

Code:
ALTER TABLE `pl_proxy` ADD `transid` VARCHAR( 255 ) NOT NULL ;
ALTER TABLE `pl_proxy` ADD `coupon` VARCHAR( 255 ) NOT NULL ;