vCSA can automatical update from the public website of VMware. But if you have a restricted internet connection you can create a local repository on a web server and reconfigure vCSA to use this link to check for updates.
to update the vCSA you use the VMware vCenter Server Appliance website:
Link:
https://<ip or dns name from vcsa>:5480
Select the tab “Update” and choose “Settings”.
Change radio button from “Use Default Repository” to “Use Specified Repository” and enter in the section “Repository URL” your URL to the server with sub directory.
Example:
http://<server ip or dns>/VI/vcsa55/upd
After that save the configuration with the button “Save Settings” - if all ok, a green message show you that the settings successful changed.
return with the button “Status” to the main update page and press button “Check Update” - during the check a message show you, that vCSA is still checking for updates
If a update is available it will show you and you can start the update installation with the “Install Update” button.
During installing all updates it show a popup message on the website.