[Koha] Looking for "How to step-by-step upgrade from Koha 3.02 Livecd version running on GNOME 2.33.0 to the latest Koha 3.6

I am running Koha 3.02.00.004 Linux GNOME which was installed by using Koha 3.2 x86 r6 livecd. I would like to upgrade to the current Koha 3.6. Can someone walk me thru step-by-step how to upgrade without loosing any data/database and important files? Thanking you in anticipation. Raphael.