To rotate: rotate()
With translate() to ensure it is at the right place.
To save: save() once you drawn the images in the sketch.

it does not save the image in the rotated form after i apply the rotate function.

rotate() won't draw the image, it just says: everything I draw after this call will be rotated. So you have to draw the image after rotate(). Look for examples of usage as it isn't the most intuitive function of Processing...

Please, read again my message: draw the image after rotate.
I suggest to look at the examples coming with Processing, search for 'rotate(' in the files.