When you first log onto the server, you should see something like
-------------------------------------------------------------------------------------
Thank you for using DigitalOcean's LAMP Application.
Your web root is located at /var/www/html and can be seen from http://108.131.197.65/
The details of your PHP installation can be seen at http://108.131.197.65/info.php
Your MySQL root user's password is vmZpCJtyE3
You are encouraged to run mysql_secure_installation to ready your server for production.
-------------------------------------------------------------------------------------
When you run mysql_secure_installation
it will ask you for the MySQL root user's password that is in the text above. It will also give you the option to set the password to one of your choosing. If you need to see the message again, run: cat /etc/motd.tail