Why rotate a layer?
There are several ways you can give your image just the tweak it needs by rotating a layer.
If you’ve added a logo as a layer to your work, you can rotate it to make sure the design looks like you want.
Creating a mirror effect? Rotate the layer with the duplicate image to line it up with the original.
Rotate a single layer of a graphic design to subtly change its appearance.
Press Ctrl+T or Command+T on Mac to open the Free Transform menu or right click on the layer and select Free Transform from the drop-down menu.
When Show Transform Controls is enabled, you can see the pivot point your layer will rotate on. Click and drag the pivot point to set it anywhere on your canvas.