In FreeBSD you usually configure your hostname in /etc/rc.conf -- it should have a line like:
hostname="myhost.mydomain.org"
Changing this will change the hostname on the next reboot. (In the meantime you can, as root, run [tt]hostname newname.mydomain.org[/tt])
To get a list of files in the current directory, the command is [tt]ls[/tt]