First check that the user have almost generate a public and a private key pair. To do that;
If there is a key do not try to regenerate keys.
If there is no "id_*" in that location you need to genarate a key pair by;
Then you need to copy your public key to the server. To do that you can use this command.
If this process sucessfully completes you can do ssh without giving your password.
Now this will connect to the server without asking the password.