Looks like you are using Express checkout.
With Express Checkout, the user goes to paypal to set the billing and shipping details, then is returned to your site and loads the pp_confirm page, the shipping is calculated when the pp_confrim page loads.
the user then has the option to confirm the order and submit it or to cancel.
With Payflow link, you need to configure your paypal account to add the Payflow Link serverice.
when you add the payflow link service, paypal will issue you the values to be used for the Login, partner, Merchant Login, User, and Password fields of the checkout wizard.
log into your account, to manage your account services and access the information for your payflow link account.