You need to import the seller's public key into your PGP program. Their public key should be listed on their seller profile. It will begin and end with these lines: -----BEGIN PGP PUBLIC KEY BLOCK----- -----END PGP PUBLIC KEY BLOCK----- You didn't mention the PGP program that you're using, so I can't give you specific instructions. Just make sure you copy the entire thing, including all fives dashes before and after the text, in the first and last lines. That's a common mistake. A single missing dash will cause the PGP program to not recognize it as a public key. Once it's imported you should be able to select that vendor as the person you want to encrypt the message to. The output will be the encrypted message, which will begin and end with these lines: -----BEGIN PGP MESSAGE----- -----END PGP MESSAGE----- Copy that whole thing, including all dashes, and paste it into the form for submitting your address. As a buyer you only need a public key if you want other people to send you encrypted messages. You must give them your public key. PGP is an asymmetric encryption system, where you always encrypt messages to the recipient's public key (although you can encrypt to your own key as well, if you want to be able to read your own messages; there can be multiple recipients).