To remove the Powered by WordPress and theme line form the footer of your theme, find the functions.php file in the root of the theme folder and comment out or remove the lines:
//$footer_content .= 'Powered by <a href="http://wordpress.org/">WordPress</a> & <a href="http://forum.bytesforall.com/">Atahualpa</a>';
NOTE: leave in the global $bfa_ata; line if you want to keep the Copyright notice.
**** STOP PRESS:
A VERY rude correspondent submitted a comment to the effect that this code is bogus and might crash your website. It didn’t for me. Perhaps a politer individual may take time to explain my schoolboy error. Of course you use the code amendment at your own risk.