This is the original article on GitHub site.

If you don’t already have an SSH key, you must generate a new SSH key. If you’re unsure whether you already have an SSH key, check for existing keys.

If you don’t want to re-enter your passphrase every time you use your SSH key, you can add your key to the SSH agent, which manages your SSH keys and remembers your passphrase.

Generating a new SSH key

1. Open Terminal.
2. Paste the text below, substituting in your GitHub email address.

   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.
   

3. 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 (/home/you/.ssh/id_rsa): [Press enter]
   

4. 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]

Adding your SSH key to the ssh-agent

Before adding a new SSH key to the ssh-agent to manage your keys, you should have checked for existing SSH keys and generated a new SSH key.