Start out with treats, as always. Let your dog see you put the treat somewhere (under a cushion, in a corner, behind a pillow, etc.) Say “Where is it?” and give an exaggerated shrug. When your dog goes to the treat, let her have it and praise her. Do this for a while, then try hiding one of her favorite toys.
Eventually, you can upgrade to people. Hide in obvious places, and show her the person she’s supposed to find. It might take a while, but after a while she’ll be able to recognize people by name and find them. Use each person’s name like a separate command. “Find George” should tell your dog to search for George specifically. “Where is he?” should apply to people in general, especially people the dog isn’t familiar with.
Have a great time teaching this trick to your dog. We have used this as a fun party game!