After you backup the configuration of vCenter Server Appliance, you can restore the backup file from vCenter Server Appliance 6.5 Installer.
Select the restore location, then Next.
Input the target ESXi host or vCenter Server, then Next.
Input the restore VCSA Name and Root password, then Next.
Select the deployment size, then Next.
Select the target datastore, then Next.
Configure the VCSA network settings, then Next.
Click Finish button, it start to deploy a new VCSA at the target host.
After finish the deployment, click Continue.
Go to Stage 2, it starts to restore the configuration into new VCSA. Then Next.
Please shut down the original backup appliance before click Finish button.
Then it starts to restore the backup.
After the restore complete, you can access this VCSA by vSphere Web Client.