Rotating light box?

Morning,

I may have missed but i am hoping you can help.

I have created my lightbox through the MakerWorld, the image was imported at an angle. It all looks good, but i want to add a base and to ensure this is right i have tried to rotate the lightbox, but cannot see how to at all within MakerWorld. Anyone able to help? Is it possible? Do i have to rotate the image in a photo editor and then re import?

thanks again