Epson 3865X Plus - Manual (Page 121)

6. Insert the card into the slot, guiding it straight down. Once
the connector pins reach the connector slot, push the card
downward firmly (but carefully) to insert it fully, as shown
below. You should feel the card fit into place.
If the card does not go in smoothly, do not force it; pull it
all the way out and try again, keeping it straight as you
insert it.
Installing and Removing Options 5-15