I don't know the context as it's a little bit vague. Does the directory / files need to be root owned? There are many options depending on what the files are and what you are wanting to achieve.
1- Change the directory / files owner (chown)
2- Create a group or use an existing group, add the user to that group and change the group ownership and permissions of the files/directories.
The above options will require root/sudo to make the initial changes. If you can give more details i.e. what the files are for as you don't want to be changing permissions and groups unless required as it could mess up other things. More info and we should be able to give more relevant solutions.
