Add a WooCommerce Checkbox at Checkout to accept privacy policy.

functions.php

<?php

/**
 * Add privacy policy tick box at checkout
 */
add_action( 'woocommerce_review_order_before_submit', 'yanco_add_checkout_privacy_policy', 9 );
function yanco_add_checkout_privacy_policy() {
    woocommerce_form_field( 'privacy_policy', array(
        'type'          => 'checkbox',
        'class'         => array('form-row privacy'),
        'label_class'   => array('woocommerce-form__label woocommerce-form__label-for-checkbox checkbox'),
        'input_class'   => array('woocommerce-form__input woocommerce-form__input-checkbox input-checkbox'),
        'required'      => true,
        'label'         => __('I\'ve read and I accept your', 'yanco_child_theme') . '<a href="'.get_privacy_policy_url().'" target="_blank">' . __('Privacy Policy', 'yanco_child_theme') . '</a>',
    ));

}

add_action( 'woocommerce_checkout_process', 'yanco_not_approved_privacy' );
function yanco_not_approved_privacy() {
    if ( ! (int) isset( $_POST['privacy_policy'] ) ) {
        wc_add_notice( __( 'You must accept our Privacy Policy.', 'yanco_child_theme' ), 'error' );
    }
}