vCenter 6.5 Upgrade - The managing vCenter Server instance is the same as the source vCenter Server Appliance that you want to upgrade......

The managing vCenter Server instance is the same as the source vCenter Server Appliance that you want to upgrade.

But then the issue is that the stage 2 of the installer wont let you edit the config there. 

Fix

1) Close the Setup and you will get a message that you can continue the install by going to https://<vcenter>:5480

2) Copy the link

3) Open a new browser and paste the link

4) Click on Upgrade 

5) Type in root password of the new 6.5 appliance and continue Stage 2 of the upgrade, by entering host name of the ESXi host where VM reside and credentials.