How do i size an image as a watermark ontop op the image?

How do i size an image as a watermark ontop op the image?

I want the watermark image to be sized… so its only 30% of the main image… is that even possible?
I have looked at the infogram… but i think i might be doing it wrong as it still fills the page…

Hello, these properties are for the position of the watermark, not for its size. The size of the watermark image cannot be changed in this step.