Step 1: Generate your key pair
First you would generate your OpenPGP key pair e.g. with gnupg. The key generation format of pgp keys is complex, but you should know that the key pair consists of a public key, which is used by the sender to encrypt for the recipient(you) and the private key, which is used by the recipient to decrypt the message.
Step 2: Share your public key and collect public keys
In the next step a sender needs the public key of every recipient. To do this step, you can give your public key to the other person using an usb stick or you upload it to a public key server.
You also collect the public keys of users you want to send encrypted mails to.
Step 3: Encrypt and send message
You write your message and encrypt it for the recipients.
You might also sign the message, which guarantees that the recipient can verify that the message has been created by you. After the encryption you send the message to the recipients.
Step 4: Decrypt message and verify signature
If you recieve a message you decrypt it and if the message is signed, you verify the signature to be sure the message is sent by the sender to whom you have the public key.
Overview: Encryption process
If you encrypt a symmetric session key is generated. With this session key your message is encrypted. After the message encryption is completed you encrypt the session key with the public key of the recipient. After that you can optionally create a hash of the encrypted message and sign this hash with your private key, this is called a signature.
After these things are done the message gets saved in the OpenPGP format.
This is a simplified answer, which does not exactly match all details of openPGP e.g. there is an encryption key pair and a signing keykey pair, but it should give you a general overview about how hybrid encryption works and openPGP works.