My mother with Alzheimer’s keeps walking from room to room yelling my name. How do I get her to settle down?

Confusion and fear are hallmarks of losing one's short-term memory. She can't see you so you "aren't there."
This is frustrating to you, but it's a phase. It wouldn't hurt to talk to her doctor about medications, but most likely the best you can do is reassure her that you are nearby. Good luck with this phase. It won't last forever, but it will be replaced by other frustrating behavior, I'm sorry to say.
Please keep in touch,
Carol