How do I modify the shipping adress on a one piece payment link?

First time ordering here! I asked for a sample unit from a seller that does sell samples but doesn't have a sample price listed on the product page itself. So I asked the seller for a one piece payment link and she gave me one.

The adress on the payment link ships to my country but its not set to the adress where im located. When I asked the seller to modify the order to ship to my adress she replied "dear, you can plz modify it online, but plz choose logistic with our shipping agent not alibaba. thanks."

How do I do that? My default adress on the website was already set right. Is this something I'll have to figure out after payment?