create public and private keys. You can just hit enter or change the options.
ssh-keygen -t rsa
Now we need to copy our public key to the servers authorized keys
cat ~/.ssh/id_rsa.pub | ssh email@example.com "mkdir -p ~/.ssh && chmod 700 ~/.ssh && cat >> ~/.ssh/authorized_keys"
Now once you’ve completed teh above you should just be able to ssh to the remote host.
If you want to be able to ssh as root. As long as the without-password option in /etc/ssh/sshd_config you should be able to do the below
sudo su cat /home/user/.ssh/authorized_keys >> /root/.ssh/authorized_keys
Now you should be able to ssh as root to the server now.