Generate and add SSH Key

Generate Your SSH2-RSA Key Pair

The SSH key will be used for connecting to instances as root user.

Open Terminal
Type: ssh-keygen -t rsa
Accept the default path and modify the file name if you wish (Enter file in which to save the key (~/.ssh/id_dsa)
Enter a passphrase and confirm (make sure this is SECURE, and noted somewhere for future reference)
Private and public keys will be generated

Download and run PuTTYgen
Click on Generate button and follow instructions displayed to help PuTTYgen generate your private public key-pair.
Once PuTTYgen finishes generating keys it will display the public key and other details in the application window.
Enter a passphrase and confirm. (make sure this is SECURE, and noted somewhere for future reference)
Click Save public key and save the key with a filename (ex: red5pro_node) on your file system in a secure location (or a common standard folder such as ~/.ssh/ under your user profile). Provide an extension of .pub to the file (public key).* Click Save private key and save the key with the same filename as the public key (ex: red5pro_node) on your file system in a secure location (or a common standard folder such as ~/.ssh/ under your user profile). Provide an extension of .ppk to the file (private key).

From the left-hand navigation menu in the Google Cloud Console, go to Compute Engine.

In the Compute Engine section,Under Settings → click on Metadata.
Select the SSH Keys tab and click on Edit.
Click on Add Item to add a New Key.
In the Public key field, Paste the contents of your SSH public key from above Generated Key.
For the key, you can use a label,For example gcp-ssh-key for easier identification.
Click Save to save the new SSH key.