Use dataset permissions to control who has access to both datasets and restricted files.
After clicking on the “Edit” button and selecting “Permissions”, choose whether you'd like to modify either “Dataset” or
"Restricted Files” permissions.
These processes are both very similar to assigning roles for a dataverse, as described here on this guide.
See the Permissions section of the Advanced User Guide for further information on granting dataset permissions and restricting/unrestricting files.