The HP Z210 BIOS will detect that a PCI graphics card is installed into the pcie slot and automatically deactivate the Integrated Intel HD2000/3000/4000 graphics. In theory, plug and play should just work :)
Obviously when you install any PCI graphics card you must also move the monitor cable from the motherboard port to the graphics card port, otherwise your still connected to the now deactivated Intel HD port which can't display as it's deactivated!
Also note, where multiple ports are available on the graphics card, one port may default to the primary port and it is this port that you must use or else the monitor will be connected to a deactivated port and you may not see the boot sequence on the monitor.
If you still can't see anything through the pcie graphics card, try another port on the graphics card (if there is one), reboot and check the screen for the boot sequence.
If you still don't see any output, ensure you are only using a straight through cable, that is DP to DP without any adapters/converters. If you have a DVI cable, try that and then try a VGA cable as last resort.
If you still have problems, try moving the graphics card to pcie slot3 and see if that results in some video being displayed on the monitor.
Failing that, your HP is likely still under warranty so i would call HP for support.