Enable Category Description on /Store/ categories

Hello,

I´d like to show category descriptions Responsive Coupon Theme 6.5.
This should work with the code:
<?php echo category_description( $category_id ); ?>
but I don´t know in what file I need to add it.

Can someone tell me where I have to put the code to make them display once there is a category description added?

It would be nice if this would be integrated in the themes already to have them enabled after updates.

Thanks,
Florian