Understanding public and private keys is the key to using PGP encryption. The user on each end of the communication must have a PGP key. Each public key is bound to an email address. The sender will encrypt the message with the recipient’s public PGP key and the sender’s signature. When the recipient receives the message, they must use their passphrase (private key) in order to decrypt the message.
The following will show how to obtain your private and public key with GNU Privacy Assistant (GPG4Win). The process is essentially the same on Apple machines. However, you are able to search public keys by email address on Apple machines (on Windows you have to have the Key ID or the public key text/file).
First, generate your own private and public key for your email address:
Follow the prompts and enter your passphrase (private key). This passphrase will be used to decrypt all messages sent to you using your public key. Once done, your screen should have the following: