Adding PCIe Video Card to Precision 3450

I had a spare AMD Radeon™ RX 550 video card that I wanted to install into my system.

Since it's a Small Form Factor desktop, the card will not fit within the cover, but I thought it should still work.

But unfortunately, the system not recognizing my video card. 

I tried seeing if there was any place within the BIOS that i can enable the PCIe Slot, because it doesn't seem like it's getting recognized at all, but there isn't a place in the BIOS where i can turn on the Slot.

Any ideas???