During reassembly, if installing the AirPort card proves challenging, you can use curved tweezers to help orient the card and insert it into its slot on the back of the logic board.

With the tweezers pointed downwards, insert the points of the tweezers through the screw holes in the AirPort card, next to its antenna connector sockets.

Using your finger, press down on the edge of the AirPort card to angle it until it is roughly parallel to the logic board.

Align the AirPort card with its slot on the logic board, and press the card into the slot until the screw holes nearest the connector align with those in the logic board.

For reference, the third photo shows the logic board removed and flipped over for a clear view of how the AirPort card is installed.