U.S. Copyright Office
They have almost everything you need available to download in PDF format, including forms and instructions. You might also want to visit Nolo Press and get one of their books on copyright law (or look for it in your library).
Because there is a charge (about $30 US) for each registration, I strongly suggest you look into registering a titled collection, which may then cover each of the contained photos as well.
However, in the US, your work is protected by copyright without registration as long as you include a proper notice on all published copies, although it must be registered before you can actually sue for infringement... |