WordPress on a cyberfusionsystem shared plan is an application you install into a site that already has PHP and a database. The panel installer is the short path. The manual path is a database, an empty directory, and the files from the WordPress project.
Create the database first and write down the name, the user and the password. Those three values go into the installer. They are not the client-area password. Mixing them up is the usual reason a site then says it cannot reach the database.
Point the domain at the account before you ask for a certificate. The delivery note on the shipping page is the same here: the certificate step waits until the name resolves to the account. That wait can be as long as 48 hours at the registry and is not an outage credit.
After the installer finishes, delete the install script if one was left in the web root, and create the first administrator with a password you do not reuse from the panel. Take a backup before the first plugin. The weekly or daily backup target on the plan is not a substitute for a copy you hold before a risky change.
This guide does not claim that cyberfusionsystem publishes WordPress. The software stays with its own project. The plan only provides the PHP host, the database, and the panel.