Updating from Version 5.03 Pro to Version 6.02

Hi, Our System Information screen shows us that we are using 5.03 Pro. and it also says "All installed packages are up to date"

How can both be true?

How do I upgrade to 6?

We are on Debian and when we run "apt-get update" and "apt-grade upgrade" it tells us we are up to date.

Our Wordpress install script is currently busted and the forum has told us that version 5 has a bug and we need to upgrade to 6....so...how do we do that?

Thanks for any help