Watermarking is now found under "watermarking" which is seen in your screen capture. It used to be found in "sharing". I think there is still some outdated help pages on the Adobe website with the wrong screen capture. Maybe that is what confused you. If you turn the watermarking on in the setting menu that you screen captured, a watermark will be added to any image you export.
You can also turn on watermarking at the time of export by tapping on the icon to the right of the share options. See my screen capture. The watermarking option is found in the second menu after you tap on this icon.