In Flow your propeller will stay "fixed", but you will insert a rotating region around it and give it the rotational value of your propeller. Under the Flow Simulation Menu / Insert / Rotating Region. You need to create a shape in your model to be the rotating region, in your case a cylinder that will be slightly larger than your propeller.
Im also trying to do a FEM analysis on the propeller, but I keep running into the same problem. In Simulation, I went to 'flow effects' and tried using my flow simulation results as an applied fluid pressure on the propeller. The fluid pressure shows in the my study tree, but when I run the solver I get the error 'no loads are applied to the model'. How might I fix this problem?