How To Reset Forgotten Admin Password OS X 10.11 El Capitan

Passwords for all user accounts can be reset and changed when booted from the Recovery Partition on OS X.
This tutorial can be used for OS X 10.11 El Capitan, OS X 10.10 Yosemite, OS X 10.9 Mavericks and OS X 10.8 Mountain Lion.

Step 1.  Boot into Recovery Partition
How To Reset Forgotten Admin Password OS X 10.11 El Capitan