In that case you can install it in either x4 or x8 slot.
I have a Dell G5 5090 PC and have purchased a Blackmagic PCIe video capture card. There are 2 black slots one above my GPU and one (Slot 4) between my GPU and the power unit. Which is best to use? 
What slot do I use to add a new PCI card for G5 5090 PC