- >Download vcenter offline ISO from vCenter portal.
- Take snapshot of your appliance.
- Login to your vcenter appliance VAMI- https://appliaceip:5480
Go- to Settings :

You must have HTTPS web server or FTPS server configured to proceed:
I am using the serv-u Management console to configure FTPS:
https://www.serv-u.com/downloads
Select Custome Repository and Enter URL and Credentials

:
Verify the Update :

Run Pre-Update Checks

You can check the affected services with this update.

Once the Precheck passed- we can go ahead with the upgrade: Click- Stage and Install

Accept EULA

You can take the vcenter backup before proceed , Same ftps server can be used to store the backups.
CLick FInish and Install


Now We have upgraded to vcenter 6.5 u3.

Validate vCenter and Delete the Snapshot.