Download and install PuTTY, a free SSH client, at the following link
Once installed, go to Windows Start menu → All Programs → PuTTY→ PuTTYgen
By default, RSA is selected. You can then click the option Generate
Wiggle your mouse cursor around the screen until the progress bar completes
You can now add an optional Passphrase to your SSH key in the middle of the screen. Add the same passphrase twice. Leave this blank if you do not want to make use of a passphrase
Once completed, select both Save Public Key and Save Private Key to save the key pairs you need.