UPDATE
1. Backup your actual installation (i.e. code and database).
2. Delete all items in your Mibew Messenger directory on the server.
3. Unpack the archive with the official distrubition in that directory.
4. Remove install.php file.
5. Restore configuration (configs/ directory), plugins (plugins/ directory),
(maybe) custom styles (if you have any), (maybe) additional
locales (if you use any), and avatars (files/avatar/ directory) from the
backup you’ve made at the step 1.
6. Visit http://<yourdomain>/<path to your Mibew Messenger>/update and follow
the instructions to update the database tables (if needed).