Where can I find the story Lord of the Flies, so I can read it on the computer?
That would be great, wouldn't it? However, as far as I know, the novel isn't available via the computer (unless your school has purchases the rights to an institution-specific e-text). It is too recent to be in the public domain like older works (Hamlet, for example), and too old to have been published in both hard and electronic copy.
The good news is, it's been published so many times and in so many editions that most libraries and used bookstores own more than one copy. (You can probably find it used online for a dollar or so.)