They have an army of flunkies to do that for them.
The Queen used to have a servant turn the pages of her newspaper for her.
Charles used to have four royal aides following him around doing such menial tasks as picking his dirty underpants off the floor, while another held a specimen bottle for him while he had a pee....
https://www.theguardian.com/uk/2002/nov/16/monarchy.jamiewilson