This tutorial will take you through the steps of changing your subscription package if you are subscribed via debit/credit card (not through Paypal). If you are subscribed using the old PayPal subscription method the process is slightly different - go to the Subscription page as below and click on
Upgrade or Renew Now
Dashboard -> Settings -> Subscription
Choose the plan you want to change to using the drop down menu and click 'Switch Plans'
You will be billed pro-rata for subscription changes. This means if you are mid subscription, the amount of time left (taken at the daily rate) will be taken off the price of your new package.