Sure! Go to your account’s Order Overview, find the order you’d like to upgrade and click on View Licenses. In the list of items, pick out the license you’d like to upgrade and click View Upgrades. All available upgrade options will be listed for you. Make your choice, click Upgrade License, go through checkout. And you’re done!
Upgrades to your license are applied immediately. Charges for upgrades are applied pro-rata, or as a 'proportion of' the full amount. The difference between your current plan's remaining days in your billing cycle and your new plan will be charged at checkout.