I have no experience with a freeboard, but I with a snowboard and Ripstick, so I'll give it a shot.
My best advice would be this; treat it like a snowboard (although keep in mind you don't have "soft" snow to land on if you fall). When I was learning how to snowboard, I treated the snowboard as if it were a Ripstick at first. Of course, I fell over and stuff, 'cause it's obviously not a Ripstick, but I was able to learn snowboarding at an accelerated rate. Once I had made the similarities to a Ripstick concrete, I treated the board as a snowboard, and learned the snowboard-specific stuff. All in all, it took me only several hours to learn basic snowboarding almost completely.
Of course, you previous experience boarding will help a ton. So just have confidence, wear a helmet, start on level ground, and go for it.