sftp is by far the easiest way to transfer a few files from one *nix to another.
On the BSD machine add
/etc/rc.conf; if you're not familiar with vi or emacs; this will work
echo 'sshd_enable="YES"' >> /etc/rc.conf. Then run
/etc/rc.d/sshd start (or reboot the machine, whatever).
On your Mac, open a console, type
sftp [username]@[BSD_machine's IP], enter your password, then
put [filename]. The file is now in your home directory on the BSD machine. Note: you must have a username besides 'root' to use sftp (add one with
adduser if you don't have one already) and it must have a password.
Also, if the BSD machine has a file you want; same thing with starting sftp, then use
get [filename] to transfer it back. Sftp works very much like normal ftp if you're familiar with that.