Getting an error "No root file system is defined" when trying to install

I am trying to install ubuntu 16 on a vultr server. But its giving me an error "No root file system is defined". I dont see where to create a partition. I am using a custom iso because its an appliance, but I tried using the ubuntu 18 install that vultr comes with and that intstalled, but then when I booted into the other iso, it still gives me the same error

Thank you