Below article Sourced from VMware Knowledge Base
We have a new video for you today detailing installing patches or updates to your VMware ESX host using VMware vCenter Update Manager. This video was created using ESX 4.0 and Update Manager 4.0. The same basic steps apply to other versions of ESX. This video also shows you how to determine how often your host checks for patches or updates, where to schedule the task, and how to run the task manually.