Installing FreeBSD is outlined here, but keep in mind, the FreeBSD Handbook is the ultimate and authoritative source on how to do anything FreeBSD, so be sure to look it over!
These steps cover both x86 and x64 versions. The screenshots reflect steps for FreeBSD 9.1, though other versions such as 9.0 or 10.0 should behave similarly.
Boot the cd with 1 (Enter or wait)
Depending on your keyboard, select the appropriate keymap
Choose a hostname for your server.
Install lib32 and System source code. You may also install Ports to save time downloading
This tutorial will uses guided partitioning.
For simplicity, the Entire Disk will be used for FreeBSD.
Hit 'yes' to erase the disk.
Review the recommended partitions and hit 'Finish'
Commit the partitioning to disk--this is the last chance to abort!
Wait for files to finish copying
Set the root password for your FreeBSD machine.
There may be several network devices. Configure at least one device, but preferably all.
Set up IPv4 by selecting 'Yes'
DHCP is used here, but selecting 'No' will permit static IPs.
Opt out of IPv6 configuration.
Regarding IPv4, ensure DNS #1 points to your gateway (likely your router)
Signify if you are using UTC (If you're virtualizing, this is set easily!)
Install at least the sshd and ntpd daemons.
Hit 'yes' to create a new user
Create a user SEPARATE from minecraft, as I have chosen 'will'. Be sure to add 'wheel' as an additional group to be invited to.
Click exit unless you wish to reconfigure any settings.
You are now done, click 'no' to proceed to reboot.
Upon reboot, you are presented with a shell login prompt--login with your newly created user!