Yes, it's possible. Enable SSH on the FreeBSD system by adding the following line to /etc/rc.conf:

sshd_enable="YES"

...and reboot. Once that's done you should be able to use putty to connect to it from the local network. If you want to be able to do this from an external machine, you need to configure the firewall that's protecting the local network to forward a TCP port to the FreeBSD systems's TCP:22. I usually set mine to something like TCP:9922 on the outside which greatly reduces the number of break-in attempts. It's amazing how effective that technique is.

Hope this helps!

J.