Installation of BigIQ on VM with existing OS

HI,

I am in the process of setting up BigIQ 6.x for testing. As a first step i have setup a VM with base OS of Ubuntu 14.04.5 LTS. Correct me if i am doing it the wrong way, does the VM need a OS as the BigIQ is a OVA file. The VM's that get proviosoned to us will have a OS, how to go about installing BigIQ in such cases. What is the BigIQ file that i need to download, there are multiple files, we have a VMWARE setup

Thanks