A question that comes up frequently is how to set permissions on a directory in InstallShield. It's actually really easy.
Go to the Application Data group, Files and Folders view in the InstallShield IDE. In the Destination computer's folders pane, find the directory you want to set the permissions for, right-click it, select Properties, then click the Permissions button. A dialog box will open where you can set a Domain, a User, and the permissions, including Full Control, Modify, Read & Execute, List Folder Contents, Read, Write, and Special Permissions. Just set what you want and that's it.