To upgrade your plan and add more credits to your account, go to the 'Account & Billing' page - there is a link in the top navigation next to the Logout link.
From that page, you can select the plan you wish to upgrade to in the 'Upgrade Your Plan' dropdown menu. When you click the 'Upgrade Now' button, you will be asked to confirm that upgrade and will be shown the immediate costs of upgrading your account as well as the ongoing future charges. You are able to cancel or downgrade your account at any time.
Errors When Upgrading
If you receive an error message when upgrading your account, please check the credit card that we have on file and make sure it is correct. You can update your credit card information from the same 'Account & Billing' page.