Installing OS X 10.9 Mavericks Developer Preview in a blank virtual machine is not supported at this time.
However, you can upgrade an already existing OS X virtual machine to OS X 10.9 Mavericks Developer Preview. To do so, please follow these steps:
If your virtual machine is running, shut it down and click Virtual Machine > Take Snapshot. If anything goes wrong, you will be able to roll back the changes.
Click Virtual Machine > Configure > Hardware > Video and set 128 MB of video memory.
Once ready, start the virtual machine and download OS X 10.9 Mavericks Developer Preview.
Double-click the installation file and follow the onscreen instructions.