Please consult to their documents or Google search.
After a Linux VPS is created, the hosting company's web platform will provide you the IP address, the SSH port number (22 by default), and what Linux version (Ubuntu 20.04 is recommended) is installed.
You should copy & paste these info into VPS Bootstrapper.
Initially there is only the 'root' superuser in a new Linux VPS, to align to good security practice, we don't recommend using that superuser to administer the system and run the websites.
So VPS Bootstrapper let's you to create a new standard user and use it to log into the VPS.