Checking for Java 6 on a Mac
I believe that the good people at Apple have now produced their version of Java 6, but that it takes a bit of fiddling to get it running for the first time.
This blog post seems to have the instructions you need.
Do please let me know if I should include anything further here, or if the above is out of date.
Once you've got the latest version of Java running, continue to download and install the program.