Hi, so do you want to update vCenter and ESXi.
For VCSA you can download the patch from VMware, mount it in the VCSA (through the VCSA Management web) and then apply it. There are more ways to do it, but this is the "easiest" way maybe.
For the ESXi to install patches, if you don't have Update Manager, you can do it by the old/cheapest way(installing the ISO file which has the patch do you want to install) or using the command line: VMware Knowledge Base
On both ways you will have to download the patches obviously, so it's up to you how to do it.
The current version of ESXi is ESXi-6.7.0-8169922-Custom-Cisco-126.96.36.199 & the latest available version is ESXi-6.7.0-9484548-Custom-Cisco-188.8.131.52. We have teh latest ISO image, so shall we mount the ISO to the blade and do the upgrade same way as we did the installation?
Thanks in advance
Yes, as this is also a Cisco's ISO, you will asure that everything should run smooth.
You mount the ISO on the balde, and then update the host.
Here you have more information about the methods available to do it: VMware Knowledge Base