Usually you doing following steps:
1) You add public key.
> ssh add -K ~/.ssh/id_rsa_next
2) Connect to server
> ssh -i ~/.ssh/id_rsa_next firstname.lastname@example.org
Do it easy!
> ssh my-server
What do I need?
One step – edit your ssh_config.
What is ssh_config? This is system-wide default SSH client configuration file. It is overridden if one is also present in the user’s home directory (~/.ssh/config).
> vim ~/.ssh/config