Open the image in Photoshop
Select the layer you want to rotate
Press Ctrl+T on Windows or Command+T on Mac
Move the cursor outside a corner until the rotate icon appears
Click and drag to rotate the picture
Press Enter or Return to apply the rotation
To rotate by a specific angle, go to Edit > Transform > Rotate
Enter the desired angle in the options bar
Press Enter or Return to confirm
To rotate the entire canvas, go to Image > Image Rotation
Choose the rotation option you want
Save the file when finished