Welcome! As you may have guessed by now, users are all the same. Each user gets a home directory. Each user can set permissions for reading, writing, and executing files and directories. And users can belong to different groups. But alas the one thing they don't get are promotions to management. Sorry!
...and to answer your question: Either login as the user whose files you wish to manage (easy) or read how to use those groups and permissions I mentioned (difficult).
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