Since vSphere 6.5, upgrading the vCSA has also been simplified. There are two ways to patch the vCSA—through VAMI, which was introduced in vSphere 6, or by using the command line. From the VMware website, download the latest vCenter Server update that's provided in ISO format and save it anywhere on your computer. The ISO image containing the patches must be uploaded to shared storage that's accessible from the vCSA that's present in the network. The ISO image can also be attached to the CD/DVD drive of the vCSA.
Before proceeding with the update, take a snapshot of the vCSA to quickly revert to a working state in case something goes wrong during the patching process.