Upgrade guide can be fond at the following link
(feng office website)/web/wiki/doku.php/installation:migration
I personally found the guide not straight forward enough.
I have completed an upgrade on one of my installs last week and here is the process I followed.
1. create a compressed file of your existing fengoffice folder as a backup (tar, zip, whatever)
2. decompress the new fengoffice installation file overrighting your existing fengoffice installation
3. In your browser, visit your.domain.com/fengoffice/public/upgrade in order to complete the database upgrade for your new fengoffice version.
-- Please note that you should also create a backup of your MySql database before upgrading by using phpMyAdmin and exporting the database to a .sql file --
