If you want to rotate some objects by a certain angle. You first need to select these objects with the Selection Tool.
Here are a few feature points related to rotation.
Move the mouse over the Rotation Handle until the mouse shape becomes a circle. Click the left mouse button, then keep the mouse pressed, and drag the rotation handle to rotate all the selected objects. Rotate to the desired angle and release the left mouse button to end.
Move the Center of Rotation: Before rotating the object, you can also move the center of rotation to another position. The method is very simple, that is, use the left mouse button to move to the center of rotation until it is highlighted. Click the left mouse button, keep the mouse pressed, and drag it to the specified position.