Just for clarity, in the ticket Marc was indicating we could not provide support for getting your 3.4.x installation working - we do support the actual 4.x upgrade.
Essentially you get your 3.4.x database in place, ensure MySQL and PHP are on versions supported by our latest release, upload our latest release files, restore your conf_global.php file, public folder and uploads folder from your 3.4.x installation, and then visit community.com/admin/upgrade/.