How to insert data using wpdb

Use $wpdb->insert().

$wpdb->insert('wp_submitted_form', array(
    'name' => 'Kumkum',
    'email' => 'kumkum@gmail.com',
    'phone' => '3456734567', // ... and so on
));

Addition from @mastrianni:

$wpdb->insert sanitizes your data for you, unlike $wpdb->query which requires you to sanitize your query with $wpdb->prepare. The difference between the two is $wpdb->query allows you to write your own SQL statement, where $wpdb->insert accepts an array and takes care of sanitizing/sql for you.