This defaults as the vendor's name and address. This cannot be changed here; you must use Maintain Vendors to change the vendor's name/address.
Tip: On the Purchases/Receive Inventory window, the vendor name appears as a link that you can click to go to the Maintain Vendors window to view or change the vendor information. If you haven't selected a vendor, you will see an Add a new vendor link that will take to you the Maintain Vendors screen where you can add a new vendor.