Insert an image and enter a caption in the Object settings window under the Text tab. Your text now appears on the image and is surrounded by a dashed frame. Outside the frame, centered above the text, is a dot. Click on the dot and hold down the mouse button. The mouse pointer appears as a crosshair. Now rotate the mouse: you will see how the text rotates.

Once the text has reached the desired position, you can release the mouse. A number appears next to the point you click to rotate the text. This indicates the angle of the rotation in degrees.

If you want to specify the angle as precisely as possible, use the Manual input. You call this up by pressing the  Ctrl  +  M  keys simultaneously. Under Rotation / Angle you can now enter the value yourself.