First of all congrats, Aussies are great dogs if given a job to do which you are going to do.

The best way to train her for sheep herding is probably to try to see if there is someone in your area who trains sheep dogs, and if they will train you and the dog to work the sheep properly...that is if she's the type of aussie who will herd, some herding breeds don't have the drive or desire to herd. As for introducing her to Candy the best way would probably be neutral territory like a park or something like that, some place were the dogs won't feel the need to protect the area.

Good luck