You can simply add the depot into VUM Download Settings. It should looks like on the screenshot below.
You have to wait for next download task or you can click button "Download Now" to start download patches immediately. When patches are downloaded you can see them in "Patch Repository".
Why someone would use DELL VUM Depot? There are two DELL software components simplifying hardware management.
First component is OpenManage (a.k.a OpenManage Server Administrator or OMSA). This component is necessary when you want integrate your ESX host with 1:many management console OpenManage Essentials or with vSphere Management Plugin called "OpenManage Integration for VMware vCenter"
Second Component is iSM - Integrated Dell Remote Access Controller(iDRAC) Service Module. It is a lightweight optional software application that can be installed on Dell 12G Server or later. The iDRAC Service Module complements iDRAC interfaces – Graphical User Interface (GUI), RACADM CLI and Web Service Management (WSMAN) with additional monitoring data.
The nice thing on VUM is that everything is done automatically based on baselines and you don't need to search what version of plugin you need for different ESX versions.
Maybe you know I work for DELL Global Infrastructure Services so I can stop here. However I often do consulting for customers running non-DELL equipment in their datacenters. Right now designing vSphere on HP Blade system and 3PAR storage. So for HP hardware you can add HP VUM depot located at http://vibsdepot.hp.com/index.xml