Facebook Activation Error

Fatal error: Uncaught exception 'Exception' with message 'Facebook needs the CURL PHP extension.' in /home/ubuntu/es.gy/html/wp-content/plugins/wpmu-dev-facebook/lib/external/base_facebook.php:19 Stack trace: #0 /home/ubuntu/es.gy/html/wp-content/plugins/wpmu-dev-facebook/lib/external/facebook.php(18): require_once() #1 /home/ubuntu/es.gy/html/wp-content/plugins/wpmu-dev-facebook/wpmu-dev-facebook.php(105): require_once('/home/ubuntu/es...') #2 /home/ubuntu/es.gy/html/wp-admin/plugins.php(154): include('/home/ubuntu/es...') #3 /home/ubuntu/es.gy/html/wp-admin/plugins.php(156): plugin_sandbox_scrape('wpmu-dev-facebo...') #4 /home/ubuntu/es.gy/html/wp-admin/network/plugins.php(16): require('/home/ubuntu/es...') #5 {main} thrown in /home/ubuntu/es.gy/html/wp-content/plugins/wpmu-dev-facebook/lib/external/base_facebook.php on line 19

I just cannot activate this. Any ideas??