To schedule an hourly event in a plugin, call wp_schedule_event on activation (otherwise you will end up with a lot of scheduled events!):

schedule_event.php

register_activation_hook( __FILE__, 'prefix_activation' );
/**
 * On activation, set a time, frequency and name of an action hook to be scheduled.
 */
function prefix_activation() {
	wp_schedule_event( time(), 'hourly', 'prefix_hourly_event_hook' );
}

add_action( 'prefix_hourly_event_hook', 'prefix_do_this_hourly' );
/**
 * On the scheduled action hook, run the function.
 */
function prefix_do_this_hourly() {
	// do something every hour
}