Sometimes OS X won’t let you change the owner of file using Finder. Annoying. Here are the simple steps to do it in Terminal.
First if you are just looking for the command it’s:
sudo chown -R _new_owner /root/to/file.txt
Where _new_owner is the name of the new owner you want to assign to the file
Now the steps:
1. Open Terminal, which you will find in Applications -> Utilities
2. Type in sudo chown -R _new_owner
3. Type the file path OR drag the file from finder onto the line after _new_owner to make the path appear.
4. Hit return
5. You may have to type your OSX login password