Keith kinda nails it, what it means from the Big Book, but people also use the phrase "turn over" to mean they turn over their problems, I think it they mean they stop trying to control things and just trust. This could be trust in your HP or trust that by doing your best things will work out, like a karma thing, what you give out you tend to receive. To me, that fits step 3 anyway, it is teh same thing really.
So, because it is step 3...I am tempted to advise you get a sponsor and start at step 1.
