you need to download the Sky Go app from the app store - Its free. Then when you start it, you will need to enter your Sky user id and password, (the same one you use on your PC). Provided you subscribe to Sky sports , and / or Sky Movies, you will then be able to view those channels on your IPAD.
As at yet you can ONLY view Sports / Movies or Sky News. On the PC you can view many other Sky channels, although Sky do say they have plans to expand the channels you can watch on idevices in the future.