The easiest way to upgrade your membership level is to:
1. Log Into Your Account
2. Go to Subscriptions in the sidebar
3. Cancel Your Account (if there is an error, you can cancel from paypal directly: https://www.paypal.com/us/webapps/helpcenter/helphub/article/?articleID=FAQ2327)
4. Go to the pricing page and sign up for the membership you'd like to have.