How to install on Shared Server (asking super user password during fresh install)

How to install a fresh in a shared server, as it asks for Super User Password to setup database

yes, that is the password you use to configure your database system and create a database for dolibarr and a database user for dolibarr.

Which platform are you running Dolibarr on?

If you have a database already provisioned and you know the passwords. dolibar table prefixes start with llx_???, yours is different. With this difference, you can use dolibarr in the same database with a single username and password.