Open a terminal session on your workstation as the user who is going to make the SSH connections to the devices.
Issue the following command: ssh-keygen
When prompted for the location to store the key pair in, you can:
Hit return, which will accept the default file name ~/.ssh/id_rsa
Using the default name may overwrite existing SSH key pairs!
Enter an absolute file path and key file name of your choice.
When prompted for a passphrase, you can
Enter a passphrase (twice)
A passphrase protects the private key file in case it gets into the hands of an attacker. On the other hand, it may be inconvenient to enter the passphrase for every connection.
Hit return in order to use no passphrase.
This increases convenience because you will be able to log in without entering the passphrase. However, it weakens security: The private key file will be unprotected if it gets into the hands of an attacker.