You can update your subscription at any time by going to your Billing & Payments page.
1) Go to the Profile menu, then click Billing & Payments:
2) Click Change Plan in the Current Subscription section:
3) Select a plan
4) Click the Update plan button to confirm and update your subscription:
On the Confirm & Update step, click the "Did you receive a promo code from us" link.
Enter the promo code, then click the Apply Code button:
Click the Update plan button to confirm and update your subscription.