1.  SSH into your instance.

2.  Edit /etc/ssh/sshd_config and set PasswordAuthentication to yes.

One way to do this is to enter the command nano /etc/ssh/sshd_config, then scroll down toPasswordAuthentication.  Change the no to yes.  Then press Ctrl+X, and press the Y key to save and quit.

3.  Enter the command /etc/init.d/sshd reload. (for Ubuntu, enter the command reload ssh)

4.  Set your password if you haven’t already, with the passwd command.

Note: This was tested with SUSE Linux.  Directory and file names may be slightly different depending on your flavor of Linux.