Hi Hans,
When you log into the portal, you navigate to My Downloads (you need to select VMware Cloud Foundation) from the menu next to you name in top right as well.
then you should see products to download, navigate to VMware vSphere and Select Solutions, patches can be found in the solution section.
Are your current VMware software licenses under a support agreement with VMware/Broadcom?
or are you running the 'Free' version of ESXi?