peebster - whilst you're learning, always start tubing from the leeward shore and kick out into the wind - as directly into it as access allows.
As the wind will be trying to blow you back on shore it'll be safer while you learn to navigate with the fins.
Sure, this won't matter on a small water, but on anything bigger than a football pitch it can save a hard carry back to the car!
The advice above about cycling backwards and adjusting the non-kicking foot is spot on - you'll soon feel when the fin is at the point of least resistance on the back-paddle and learn how to spin, all it takes is a wee bit of practice.
I wish I'd sent my bro out without a rod the first time he tubed, it was all a bit too much for him and he didn't enjoy the fishing or the tube. Good idea to just muck about in the water until you're comfortable.