Creating A link for downloading files listed in directory

HI,

We know that when we list a directory structure, all the details that is
subdirectories and files are shown.
When I click on the sub directory it links to the next dub directory and
works fine.
My problem arises with the files listed, when I click on the link to
files I should download that file which I have clicked on

Please tell me how would I accomplish this .

Thank you