You just put "HDD" or something in the boot order field and then mark the virtual drive you are trying to boot from as the "boot" drive in the "Virtual Drives" tab in CIMC under the storage controller.
When you install VMware you tell it which virtual drive you want to install to and this should be the same virtual drive the server boots from.
If you are still having issues, post screen captures of where you are at and what you are seeing.