How do I find out my password to my mac mini?
Or how do I reset it?

If there is a second administrator account on the computer you can reset it through the "System Preferences""Users and Groups".
Here are some websites about resetting a lost password.
Reset your lost OS X password (http://lifehacker.com/278898/reset-your-lost-os-x-password)
https://kb.wisc.edu/helpdesk/page.php?id=3853
How to reset your Mac OS X password without an installer disc | MacYourself (http://www.macyourself.com/2009/08/03/how-to-reset-your-mac-os-x-password-without-an-installer-disc/)