generate_ssh_key

Open Terminal.

$ ssh-keygen -t rsa -b 4096 -C "your_email@example.com"
This creates a new ssh key, using the provided email as a label.

Generating public/private rsa key pair.
When you're prompted to "Enter a file in which to save the key," press Enter. This accepts the default file location.

Enter a file in which to save the key (/Users/you/.ssh/id_rsa): [Press enter]
At the prompt, type a secure passphrase. For more information, see "Working with SSH key passphrases".
Enter passphrase (empty for no passphrase): [Type a passphrase]
Enter same passphrase again: [Type passphrase again]

Start the ssh-agent in the background.

$ eval "$(ssh-agent -s)"
Agent pid 59566
If you're using macOS Sierra 10.12.2 or later, you will need to modify your ~/.ssh/config file to automatically load keys into the ssh-agent and store passphrases in your keychain.

Host *
 AddKeysToAgent yes
 UseKeychain yes
 IdentityFile ~/.ssh/id_rsa
 
Add your SSH private key to the ssh-agent and store your passphrase in the keychain. If you created your key with a different name, or if you are adding an existing key that has a different name, replace id_rsa in the command with the name of your private key file.

$ ssh-add -K ~/.ssh/id_rsa

$ pbcopy < ~/.ssh/id_rsa.pub
# Copies the contents of the id_rsa.pub file to your clipboard