What HandySolo means (I assume) is that you're going to have to edit your plugin manually. I've done exactly what you are trying to do on my personal blog. Edit your Share-This plugin so these four lines look just like mine:
@define('AKST_ADDTOCONTENT', false);
// set this to false if you do not want to automatically add the Share This link to your content
@define('AKST_ADDTOFOOTER', true);
// set this to false if you do not want to automatically add the Share This form to the page in your footer
@define('AKST_ADDTOFEED', true);
// set this to false if you do not want to automatically add the Share This link to items in your feed
@define('AKST_SHOWICON', true);
// set this to false if you do not want to show the Share This icon next to the Share This link
Then, you'll have to edit your single post template and insert this piece of code where ever you want the Share-This link to appear:
<?php akst_share_link(); ?>