To install software updates on OS X: > Software Update
If the Apple Java update is not offered, then you don't have Java installed, or you're on a release of OS X prior to 10.6, or you're using a local Software Update Server or local Reposado server and it hasn't cached the Apple upate yet. (And if you don't know what the Software Update Server or Reposado servers provide, then you're probably not one of those.)
Here's the most recent Apple update on this: About the security content of Java for OS X 2012-003 and Java for Mac OS X 10.6 Update 8 (HT5247)
This particular Java 2012-003 download apparently hasn't reached the Apple downloads servers yet, based on some of the chatter, so there's not yet a place to download it other than via Software Update.