I'll do my best to explain using words only since I don't have access to a photo of the stock engine bay on me (I did... at some point in time; so if you're really stumped I'll go digging for it).

Basically open the hood, and stand facing the front of the car (i.e. in Australia, steering wheel should thus appear to your left). On YOUR right, about halfway in the middle, there should be a black box with silver clips around it. It's about the same size as the panel filter you purchased. Undo the clips, which may be a bit hard at first if they haven't ever been opened before (and they could be hot). When you've opened all the clips, the lid to the box will slide off and you will see the existing air filter (it should be white from memory but again, colours do change with usage!). Simply take it out by lifting it up, and taking note of where the cut-off corner is, insert the K&N filter in the same direction*. Make sure the fit is right/tight/etc and then put the lid back on and close all those silver clips. Viola! you're done.

Whether or not you'll notice a significant difference is questionable but it's supposed to allow you to rev more freely. It'll sound slightly different too when you rev.

* Note: I am presuming you don't need to re-oil the K&N filter since they come factory pre-oiled when new.