Select the object you want to rotate in the Scene View.
Click Item Tools tab Transform panel Rotate .
Use the gizmo to rotate the currently selected object:
Before you can rotate the currently selected objects, you need to position the origin (center point) of the rotation. To do this, place the mouse over the arrow at the end of the desired axis. When the cursor changes to , drag the arrow on the screen to increase/decrease the translation along that axis. This will move the gizmo itself.
Dragging the ball in the middle of the rotate gizmo enables you to move it around, and snap it to points on other geometry objects.
Once the rotate gizmo is positioned correctly, place the mouse over one of the curves in the middle, and drag it on the screen to rotate the selected objects. The curves are color-coded, and match the color of the axis used to rotate the object around. So, for example, dragging the blue curve between the X and Y axes, rotates the objects around the blue Z axis.
To rotate the orientation of the gizmo to an arbitrary position, hold down the CTRL key while dragging one of the three curves in the middle.
To snap the gizmo to other objects, hold the CTRL key while dragging the ball in the middle of the gizmo.