Grant 100 extra points for every successful checkout.

extra-checkout-points.php

<?php

/**
 * Grant 100 extra points for every successful checkout.
 */

add_action( 'woocommerce_checkout_order_processed', 'wc_test_add_points', 10, 3 );
function wc_test_add_points( $order_id, $posted_data, $order ) {
	WC_Points_Rewards_Manager::increase_points( $order->get_user_id(), '100', 'customer-checkout-out' );
}

add_filter( 'wc_points_rewards_event_description', 'wc_test_event_description', 10, 3 );
function wc_test_event_description( $event_description, $event_type, $event ) {
	if ( $event_type === 'customer-checkout-out' ) {
		$event_description = 'Extra Checkout Points';
	}

	return $event_description;
}