How to get the search bar to work correctly

I'm needing to be able to get a search bar to work in PHP using HTML. I have done some coding, but cannot fully grasp how to do it. What can I do to get the search bar to work? I am needing to be able to search for a last name and have it display the name. There is no set first name or last name, just the name of the person all in one (if that makes sense)
I have attached the files that I am using.

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