Make a backup of the database tables and all files.
Using your current config.php as a guide configure the new config.php's settings, PHP-Nuke 6.5's config.php has a new variable: $sitekey, it is recommended that
you change at least some of the letters/numbers in it to make it unique.
Upload all files and folders included in Nuke's html folder so that they replace your current files.
Upload upgrade60-65.php to Nuke's main directory (where config.php is) and point your browser to it. Delete it once done.
If you were using Splatt forum with Nuke 6.0 and wish to transfer its data into the new bbtonuke forum, use NSN_Move