Juniper QFX5100 Series book has pretty good coverage of VCF related topics, but I think VCF feature guide is better suited for lab preparation.

Unfortunately I don’t have real QFX5100 gear, so my VCF study would be completely theoretical. But the good news are that all that complexity of VCF has nothing to do with end user, and to just configure it is a pretty simple task. Definitely no rocket science…

VCF can be configured in two different ways: autoprovisioned and preprovisioned (technically there is also a nonprovisioned mode, but it is not recommended and therefore not expected on the lab). The only difference between autoprovisioned and preprovisioned modes – in autoprovisioned mode you need to configure only spine device serial numbers, but all devices needed in preprovisioned mode.
Examples:

Also there is configuration statements to enable autoupgrade and disable split detection:

And not forget that VCF has virtual management interface:

But the really useful commands should be those that allow you to check VCF status and reconfigure it (because I expect that on the lab VCF will be preconfigured, but broken in somewhat weird way).

So first some show commands:

Command names are self-explanatory, except for the last one – this command allow you to check, to which physical device in VCF you have console connection – should be really useful for checking correctness of VCF configuration.

And finally some request commands:

Make sure you have complete understanding of all this commands, various ways to make, break, check and repair VCF.

After configuration VCF is just a big switch, nothing special except for the port names (but I think you already should have a good understanding of Junos port naming conventions if you thinking about JNCIE-DC lab).