You've requested the ability to pay with PayPal. You've requested to pay in advance. We just released both in one simple feature.
Go under "Settings" then "Account"
Click the "Pre-Pay with PayPal"
Select one of the suggested amounts to pay (there is also an "other" option to allow you to enter any number you like)
Log into PayPal
Once logged in you can select any funding source you like (so yes that means you can pay with eCheck, Credit Card, etc.)
Look at your new account balance