Apple SDRAM DIMM - Manual (Page 6)

6 - iMac (Slot Loading)
11 Use a coin or screwdriver to close the latch on the access door.
12 Gently turn the computer right side up.
13 Reconnect the cables you disconnected from your computer.
14 Press the power button on the front of the computer to turn it on.
Repackaging the DIMM
If you are replacing memory as part of the Customer Installable Parts
program (rather than upgrading memory), repackage the SDRAM DIMM
you removed from the computer in the static-proof bag and box that you
received with the replacement SDRAM DIMM. Seal the box with the tape
included, and affix the return label.