I'm a beginner user of fluent & gambit programs. My task is to perform simulation of fluid move caused by impeller's rotation. I'm looking for anyone able to describe step-by-step the procedure I have to follow in both programs to get such simulation.

See Fluent Help File in this topic: "10. Modeling Flows with Rotating Reference Frames"

and in particular: "10.7 Setting Up a Single Rotating Reference Frame Problem ".

You need to set the fluid zone as Moving reference frame.

If your container is cylindrical with the impeller exactly at the center (without offset), you can use the single reference frame. For this you don't need any special effort in Gambit. But if you have irregularities in the container wall, or if the impeller is with an offset or at an angle, you need to create separate zones in Gambit itself. (Basically two concentric zones: one central cylindrical zone containing the impeller, and the second annular region surrounding it).