First you will need to download GPG Suite (https://gpgtools.org/) and run the installer.
The installation should only take a minute or so, once completed you will notice an app called GPG Keychain has been started. This is the GUI in which you will handle all of your PGP tasks. You may notice an icon in your dock, it is a key chain.
Let's send our first encrypted message, first we are going to need somebody to talk to. I guess for this example we can assume you're about to send your address to a vendor. On the order page, click the PGP tab, and copy the vendors entire Public PGP key to your clipboard.
Once their key is contained within your clipboard, open TextEdit, paste the key and save the file as a plain text file with .asc extension. Then back on the GPG Keychain click on the "Import" button and then select the file you just saved;
If everything worked out you will see a window stating the certificate was imported successfully.
Now we need to prepare the message, so in this case it will be your address. Open up a fresh plain TextEdit document and type in your correctly formatted address and any additional information. Once done, select the entire message and go to Services > OpenPGP: Encrypt Selection.
Back on GPG Services window, select the recipient that you intend to send the message to, as we imported their public key they will be somewhere in your list. Once your recipient has been selected, click Encrypt.
If all is well, you will see that the text in TextEdit was replaced with a PGP message. Great, your encrypted message is ready to be sent to the vendor!
In TextEdit, select the text you want to decrypt, right click on the selection and then under Services click on OpenPGP: Decrypt Selection.