I would think you mean PCIE Not PCI. If you do mean PCI then thats a very old PC
A PCIE card has a J shaped hook like end to it.
You should line the card up in the slot straight and even then applying firm gentle pressure push it into the slot. You should hear a click as the card seats itself into the clip at the back of the slot. Now put the screw in at the connector end and job done.