Upgrade to Pro
If you already have an account and would like to upgrade to the Pro plan, head on over to your Profile page and look at the "Account Plan" section.

Clicking the "What do I get with Pro?" button will bring you to the
upgrade page which explains the difference between Basic and Pro, and also lists all of the Pro features.

Click the "Upgrade!" button to go to the SSL-secured payment page and input your information. If successful, you will instantly upgrade to Pro with a 7-day free trial.
Signing up for Pro
If you don't have an account already and would like to sign up for Pro, go to the
plans page and click the "Sign up!" button under the Pro column.