I'd start by taking a look at the system configurations page if you are downloading Java 5.
http://java.sun.com/j2se/1.5.0/system-configurations.html
Here are the installation notes for linux. There's a review of how to install both the self extracting binary and the rpm file.
http://java.sun.com/j2se/1.5.0/install-linux.html
And a search of the forums and/or Google yields several results which may be helpful to you.