You can't extend an array from within the controller, only OMSA and tools.
While it is true you can install using Vsphere, there are other ways to load the OMSA VIB. You can also download the VI remote CLI tool, if you enter the ip of the host on the ESXi Welcome page that comes up is a link on the right hand side.
Download the CLI tool if not already installed. Download this (VIB file) - en.community.dell.com/.../download.aspx
After that you can install the VIB bundle like this -
1. Copy the OMSA 6.5 VIB to the ESXi host (/var/log/vmware or /vmfs/volumes/<datastore>)
2. Run the following command from the vSphere CLI prompt:
esxcli.exe --server <server> software vib install –d <remote path to VIB>
C:\Program Files\VMware\VMware vSphere CLI\bin>esxcli.exe --server 10.10.10.10 software vib install -d /var/log/vmwar/Dell_OpenManage_ESXi_OM650-offline_bundle-467660.zip
Enter username: root
Message: The update completed successfully, but the system needs to be rebooted for the changes to be effective.
Reboot Required: true
VIBs Installed: Dell_bootbank_OpenManage_6.5-0000
3. Reboot, Check Software > Advanced Settings for UserVars.CIMvmw_OpenManageProviderEnabled should already be set to 1
Now the VIB is loaded on the host.
To Use -
1. Download OpenManage Server Administrator Managed Node version 6.5 from Dell’s support site (not the OpenManage Server Administrator Web Services under the ESXi downloads)
2. On a separate windows machine install OpenManage Server Administrator Managed Node and choose ‘Custom’ install.
3. When choosing features make sure Server Administrator Web Server is selected (If installing on a desktop it could be the only option).
You can then launch with icon on desktop, enter host ip and login information. Accept certificate and your done installing OMSA.
Then you can access the controller page, then VD on OMSA and reconfigure with new drives to extend.
I am also emailing a detailed walkthrough to your email.
Let me know how it goes.