A keypair is a certificate used for identification in SSH. Amazon has a feature where it will put the public component of a keypair onto an instance during startup. So, as long as you have the private part, and your Security Groups are configured correctly, you can SSH into an instance.
- Browse to the Key Pairs part of the Console.
- Call it "zerotocloud".
- It’ll be downloaded to your Downloads directory automatically. If using a non-default Downloads directory, you will have to adjust some later steps.