PayPal Standard where do I add shipping fields to pass through to PP history log?

[plumworks]

Have existing osCommerce store someone created with PayPal Stanard. I need to edit to pass through fields (e.g., first_name1="") so it shows up in PayPal history log and Shipping Center labels.

 

Which osCommerce webpage do I post this on, and anywhere in particular?

 

Thanks!