If you know anybody who fishes and knows their stuff you should ask kindly ask them to take you out with them and share some of their knowledge with you. You'll save heaps of time learning from someone else. If i had a friend who fished and was as keen as i was who could show me knots, locations, baits, species, times... the lot, probably would have saved me a lot of lonely cold days catching nothing All a learning process!
As people have said above, Narrabeen lake is a good starting point. Chockers full of fish and a nice easy place that's safe. Heaps of undersize so you might not catch monsters but it's excellent to learn the basics - knot tying, baiting up, casting, setting the hook etc. before you more up the ranks a little. It's where i learnt to cast as a kid!
Good luck. Members here are more than happy to help