i am using siri on ios 6 gm right now all you have to do is download and install ios 6 and it asks you during setup if you want to enable or disable siri. that is all there is too it works right out of ios 6.. press down on the home button for siri to appear. hope that helps!
Could someone else with Siri on iPad ask her to say "Liam". On my iPhone she pronounces it correctly. But on my iPad she says "Lie-am" instead of "Lee-um".