Be sure you have made a backup of your web server files AND of your MySQL database too. Do this everytime you change something that might fail. It is very important that you store your custom files like conf.inc.php, frontend.css, conf.template_default.inc.php and startup.html.

Download the most current release of phpwcms. If you have not installed every release, download and install every available patch released. But you can also download most current core package.

It is very important to check if the database has been extented or changed in the release you want to install. The best is to do it manually - please remember to check your database table prefix when you update or change something. It is also possible to try the upgrade.php in setup folder - remember that you have a backup of your working files and database!!!

You should download the patch files or core release to your local disk and uncompress it. Then use your ftp client to upload every new file. Do not upload config or custom files like descrived above. If there are changes please download these files from your webserver and edit locally - then put files to your webserver again. It's much easier to check for changes if you do it this way.

Please check forum to find an answer.