Boot up FreeBSD, when you get to the FreeBSD boot menu select “Boot FreeBSD in single user mode”
When you get to the following prompt hit enter.
When prompted Enter full pathname of shell or RETURN for /bin/sh:
You will now be booted in single user mode.
Run the following commands to mount the root drive as read and write.
mount -u / mount -a
Now reset the root password with passwd
Your now finished. You can type in “exit” to continue booting, or you can just reboot.