Hi,

1) Go to your theme functions.php file and register new 5 minutes schedule interval:

// Adds 5 minute schedule interval
add_filter('cron_schedules', function($schedules) {
    $schedules['five_minutes'] = array(
        'interval' => 300,
        'display'  => esc_html__('Every Five Minutes'));
    return $schedules;
});

2) Open file stachethemes_event_calendar\assets\php\install\activate.php

edit line 44:

wp_schedule_event(time(), 'hourly', 'stec_cronjobs_hourly');

to:

wp_schedule_event(time(), 'five_minutes', 'stec_cronjobs_hourly');

3) Deactivate and Re-activate the calendar from Dashboard -> Plugins.

Now your hourly schedules will run every 5 minutes.

NOTE: Please read how wordpress cron works here: https://developer.wordpress.org/plugins/cron/

Tldr: WP-Cron does not run constantly as the system cron does; it is only triggered on page load.

To make your cron jobs "real" cron jobs check this article.