Hi,

Open your theme or child-theme functions.php file and at the bottom add following hook:

add_action('wp_footer', function() {
    ?>
    <script type='text/javascript'>
        (function ($) {
            if (null === document.querySelector('.single-stec_event') || null === document.querySelector('.stec-event-submission-form')) {
                return;
            }
            $(document).on('click', '.stec-builder-form-modal.stec-success .stec-style-button', function () {
                
                // REPLACE VALUE WITH YOUR CALENDAR URL
                var linkToMyCalendar = 'https://link-to-my-calendar-page';
                
                window.open(linkToMyCalendar, '_self');
            });
        })(window.jQuery);
    </script>
    <?php
});

replace 

https://link-to-my-calendar-page

with your actual calendar url