Copy the gold_cart_files directory into the wp-content/uploads/wpsc/upgrades folder. 

This folder should be automatically created when the e-commerce plugin is activated, but if it is not, you will have to create it yourself.

Now a new panel should appear in the Upgrades page where you must enter your API Username and API Key.

For more information visit our documentation page or visit our online forums.

http://www.instinct.co.nz/e-commerce/docs/