How to add shortcode between post content and plugins

Hi,

Example page: http://www.atlasandboots.com/checking-my-privilege

I recently changed to Sela and am still trying to work things out. I want to add something (namely a shortcode for a PayPal donate button) between my post content and the plugins at the bottom (AdSense, Related Posts, Facebook Comments). Normally, I would edit single.php and manually add in the code but in Sela it seems to work differently. I’ve tooled around with content.php but just can’t figure out how to get to the area between the text and the plugins.

Any help would be much appreciated!