I'm not able to find the help documentation page you are referring to. The help page that comes op on the payment gateway section of the checkout wizard in eCart 5 just has information about local and remote checkout. no examples of the api information.
With express checkout, there are 3 server behaviors that get applied:
On the Checkout page:
1) Authentication For PayPal Express Checkout
On the pp_confirm page:
2) Get Payer Profile For PayPal Express Checkout
3) Process Transaction with PayPal Express Checkout.
you need to update the API information in all three of these server behaviors.