We can use insert query in wordpress as follows.Just take a look on query.It is quite simple as we use in php to insert data into database.
<?php global $wpdb; $wpdb->prepare( "INSERT INTO `wp_submitted_form` (`name`,`email`,`phone`,`country`,`course`,`message`,`datesent`) values ('$name', '$email', '$phone', '$country', '$course', '$message', '$datesent')" ); ?>
Or,
use can use query in this way also
<?php $wpdb->insert('table_name', input_array()); ?>
like
<?php global $wpdb; $wpdb->insert("wp_submitted_form", array( "name" => $name, "email" => $email, "phone" => $phone, "country" => $country, "course" => $course, "message" => $message, "datesent" => $now , )); ?>