CHECK THIS ERROR PLUGIN

I am getting the following error when the plugin active

Notice: A session had already been started - ignoring session_start() in public_html/wp-content/plugins/comments-plus/lib/class_wdcp_model.php on line 44

Notice: Undefined index: wdcp_google_user_cache in public_html/wp-content/plugins/comments-plus/lib/class_wdcp_model.php on line 63

Notice: Undefined index: wdcp_twitter_user_cache in home/agenc391/public_html/wp-content/plugins/comments-plus/lib/class_wdcp_model.php on line 87

Can anyone tell me how to fix