Add mailchimp subscribe to woocommerce checkout.

config.php

/**
 *  Subscribe User to MailChimp
 */
function wooms_mailchimp_subscribe_user($order_id,$posted){
    if(!empty($_POST['wooms_susbscribe'])  && $_POST['wooms_susbscribe'] == '1'){
        try{
            $email = $posted['billing_email'];
            $merge_vars = array('FNAME' => $posted['billing_first_name'],'LNAME' => $posted['billing_last_name']);

            $api = new MCAPI(mailchimp_api_key);
            add_post_meta( $order_id , '_customer_opted_in', 'yes');

            $retval = $api->listSubscribe( mailchimp_listid, $email, $merge_vars, $email_type='html', mailchimp_double_optin);

            add_post_meta($order_id, '_mailchimp_subscribe_result', $retval ? "true" : "false");

        } catch (Exception $e) { add_post_meta($order_id, '_mailchimp_error', json_encode($e)); }

    } else if( !empty($_POST['wooms_susbscribe'])  && $_POST['wooms_susbscribe'] == '0' ){
        add_post_meta( $order_id , '_customer_opted_in', 'no');
    }
}
add_action('woocommerce_checkout_order_processed','wooms_mailchimp_subscribe_user',10, 2);

/**
 *  Display Newsletter Checkbox on Checkout
 */
function wooms_add_newsletter_checkbox_to_checkout(){
    ?>
<div class="form-row wooms">
    <input type="checkbox" class=".input-checkbox" name="wooms_susbscribe" id="wooms_susbscribe" value="1" checked="checked">
    <span class="wooms_label">Yes, I'd like to receive email updates and special offers!</span>
</div>
<?php
}
add_action('woocommerce_review_order_before_submit','wooms_add_newsletter_checkbox_to_checkout',99);

Hi!, Thanks for this! Pasted it in the functions.php file and it works fine. But what do i have to do now? where can i call the action for putting the subscribers' email into my mailchimp list? I know it's something with the mailchimp_api_key but i don't know how to call this one. Or am i wrong? Sorry for this kind of rediculous question but i'm new to this and i try to get this working...
cheers!