LittleR:
c) upgrade the database to the new version
The zc_install script is used to do this in an automated way. Just a couple clicks to take care of keeping all your data intact and bringing its data structure up-to-date to work with the new version.
i don't know how to use the zc_install script.
So, based on the information provided so far, the ZC 1.5.3. Hotfix #1 files have been uploaded to the server. The admin directory is named admin and there is a folder named zc_install. At this point, there is no configure.php file in includes or admin/includes. But there is a dist-configure.php file.
Ideally you have created a new blank database to which the old data can be transferred/copied so that the original store can continue to operate unhindered.
Even if there were configure.php files, as long as the folders are named as above, the site and the admin can not be accessed by design.
So, if you then goto the website/pathofnewZCsite/zc_install you will be presented with the information to step through the installation of ZC... Once that process starts, most of the information/questions have help statements or clarifications adjacent to the area... It is difficult to explain from that point what is not understood without knowing what is confusing. As going through, either take note or just shoot a question to the forum and the confusion can be cleared up.
ZC Installation/Maintenance Support <- Site
Contribution for contributions welcome...