Go here and find screenshot instructions on how to file online: photoattorney.com
For a whole lot more detail, including Photoshop action information to format images and special tips and tricks (not to mention very solid legal information on copyright), get this book:
http://www.amazon.com …oks&qid=1303778654&sr=8-1
I really, really recommend that book.
Briefly:
A "collection" is any logical categorization you want to call it. "My images of 2010" is an allowable collection.
You have a 3-month "grace period" after an image is published that you're protected until you get the registration sent in. In other words, if you publish an image today and someone immediately infringes your copyright, you have 3 months (not 90 days...three calendar months) after publication to register it and act against that infringement. "Published" means you've delivered the final images to the client; just showing the proofs is not published. "Published" means you've put them on Facebook or an unsecured website; having them on a password-secured website is not published.
Many busy professionals make use of the 3-month grace period by simply sending in everything they've done in the previous three months in one registration, like "John Doe Photography 2011-1qtr." They just do it regularly, four registration applications a year, to cover everything.
Registering published work differs from registering unpublished work in that you must register published work in a separate registration application from unpublished, you're limited to registering only 700 images in on one published work registration application (no specified limit for unpublished work), and each image in a published-work application must have some kind of unique name, like "2011-04-21_Jane_Doe_1234.jpg"--not a headache for digital files.
There is no specified file size. The image merely has to be large enough to identify what it is. Remember that copyright covers "derivative" work, so minute details aren't important (I set my jpegs to 600 pixels on the long side, 72 ppi, saved at Photoshop quality 5), zipped. The only limitation is in how many you can upload within the hour the online system allows you, but there is a workaround: You can run multiple 60-minute upload sessions for one registration by creating several zips, each small enough to be uploaded in a 60-minute session, and putting them in separate queues.
In other words, you can conceivably upload thousands of unpublished images in one application: "My Life's Work 1972-2011."