Acer AT350 F1 - Manual (Page 77)

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Caution: Do not discard the slot cover. If the expansion card is
removed in the future, the slot cover must be reinstalled to
maintain proper system cooling.
Remove the expansion card from its protective packaging,
handling it by the edges.
8 Insert the card in the selected slot (5) making sure that the card is
properly seated.
9 Insert the screw holding the card in place (6).