Choose Home tab→Modify group→Move Faces list→Rotate Faces 
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Select the faces you want to rotate, then click the Accept button.
Define the axis of rotation.
Type the rotation angle you want.
Finish the feature.
Tip:
You can use the Select option on the command bar to specify whether you want to rotate individual faces you select, a set of faces that belong to an existing feature, or an entire body.
You can define the axis using surface geometry, such as a cylindrical or conical face, or by selecting two keypoints that define the axis you want.