It's on the other side of the station i.e. not the road side the other side.
Just follow the stairs up, follow it to the far left and down the stairs.
It arrives just under the stairs there. Usually there's a couple of people waiting.
Yes Campbelltown does have a Uni Bus and its generally on time. You can pick up a timetable from the UWS Student Association building.
Also when catching the shuttle bus from Campbelltown factor in a bit more time to get to the campus because it doesn't do a straight run.
The shuttle buses route is:
Campbelltown Station -> Macarthur Square -> Building 2 -> Building 21.
The first stop 'Building 2' would be your best bet getting off if it is your first day at Campbelltown Campus as its closer to most sought after buildings i.e. the Library, Student Centre, Cafe etc.
Hope this helps,
Anthony.