Dell OptiPlex 755 User Manual page 106

8 Place the card in the connector and press down firmly. Using the following illustration as a guide,
ensure that the card is fully seated in the slot.
106
Expansion Cards
2
1
1 PCI Express x16 card
2 release lever
3 securing slot (not all cards)
4 securing tab
5 PCI Express x16 card connector
3
4
5