If you already have the drivers, good. If not download them. When only 1 monitor is plugged in the Display Setting will only show 1. Now if you plug in a 2nd monitor and restart you should see 2 monitors. Download your hp drivers from HP Support & Drivers
and just type in HP176 and install all the drivers that them may have for you. Check if you PC has 2 vga ports out so you can do dual screen. If you have an integrated video card then you will need a PCI card for dual monitors unless you have a PCIe or VGA slot on the motherboard.