You can set access permissions for a file or directory using Plesk control panel as follows:
- Login to your account in Plesk and click on File Manager.
- Locate the file or directory for which you want to set access permissions, and click on the arrow. Click on Change Permissions in the drop-down menu.
- Next, you will be able to modify user permissions by selecting the Allow or Deny checkboxes. If you need advanced permissions, click the Advanced button.
- In the advanced page, you will have a set of permissions to control for each user, also you can choose which folder these permissions are applied to.
For more information, you can check Plesk Documentation