All domains are renewed automatically as long as you have valid credit card details in your iwantmyname account and you have not turned off auto-renewal. No other action is required.
If you did turn off auto-renewal but want to keep your domain, login to your account and go to your dashboard. Click on the domain name you want to renew, and then click on the green renew button on the following page. As long as the billing can be processed, that will be done, the renewal will get started, and you will be emailed a notification and receipt. If there's any issue, you will be emailed about that instead.
You will be notified well in advance of your domain's renewal and billing. We will also notify you if we cannot charge the credit card on file. This will give you plenty of time to resolve any issues before the expiry date.
As soon as you receive a renewal payment notification and receipt you can rest assured that your domain renewal will automatically happen on time.
If the domain has been billed for renewal but has not yet renewed, and you do not want to keep it, please login to your account and contact us via our support form and we can usually cancel the renewal and issue a refund on the renewal billing.