Fatal Error with Ad Squares Widget

Hi! I tried logging into my site admin but I can’t login because of this message:

Fatal error: Cannot redeclare ws_widget__ad_squares_activate() (previously declared in /home/autisms1/public_html/blog/wp-content/plugins/ad-squares-widget/includes/functions/activate-deactivate.inc.php:30) in /home/autisms1/public_html/blog/wp-content/plugins/ad-squares-widget/includes/functions/deprecated.inc.php on line 23

I guess I have to fix it through php admin panel but I know very little about php. Can someone please help explain to me what this is and tell me how I can fix this? Thanks in advance! Your expertise will be greatly appreciated.