The PayPal Payments Advanced option uses the Paypal Payflow Flow Pro access.
when yo sing up for a Payflow pro account, the generate a Username, Partner, Vender and Password.
These should be used for the Partner, User, Merchant Login and Password settings.
Payments Advanced replaces the older systems in place, if you call paypal at this number you will be able to sign up for a paypal advanced account which is only $5 a month:
more details about paypal payments advanced can be found here: