When a file is under restricted access, no users can download the files directly and only repository users can submit a request. You can also specify which repository user can access the file beforehand. To set up a file access restriction, follow the steps below:
Login and go to your dataset page. To locate the page of your dataset, follow steps here.
Under the Files tab, select the file(s) that you would like to restrict access, then click Edit Files > Restrict.
Check Enable access request and (optional) input the Terms for Access for Restricted Files, then click Save Changes.
After this is set up, other users can no longer download the restricted files. When they click on Request Access, you will receive an email with a link for granting them access.