Enabling the root account to access ssh directly is a major security risk. However, you can enable it if you like to do so by doing the steps below:

1. Edit the sshd_config file by sudo vi /etc/ssh/sshd_config

2. Find the line PermitRootLogin no and change it to PermitRootLogin yes.

3. Restart the ssh service by sudo /etc/init.d/ssh restart or sudo service ssh restart

You have now enabled ssh using the root account.