In order to install vCenter server you need to install vCenter Inventory Service first. To install Inventory service you need Vmware vCenter single sign on (SSO).
Run the Installer
Accept the Licence agreement
Decide the location to install
Enter the FQDN for the inventory service
Enter the appropriate port numbers manually or keep the default.
Choose the inventory size.
Enter your Single Sign On (SSO) username/password and lookup service URL
Click Install Certificate
Click finish to complete the installation
congratulations !! vCenter Inventory Service is installed now. The next step is to install the vCenter Server.