"chown" is a command for changing the users and groups who own a file. But the options "775 xyz" are used with chmod, a command for changing what permissions the owners and groups have over a file. I'm not sure what you're trying to do so I can't tell what part of the command is wrong.
Either way you can run a command with elevated permissions by putting "sudo" in front of the command. Or by switching to the root user by using the command "su" or "sudo -i" (if you have sudo access, but don't know the root password)