OK, BEFORE you touch the memory with your bare hands, make sure that you know how to handle it and not zap it with static electricity. RAM is VERY sensitive to static. You can easily kill a stick with a woolen jumper if you want to.
ONLY hold the RAM around the edges, never on the flat sides and NEVER EVER on the components or pins.
It is preferable to leave the computer plugged in, but turned off at the mains/PSU if possible. This keeps the computer grounded at all times
If you have a grounding strap, wear it (and plug it in).
After disassembling the case, ground yourself on the bare metal of the case by just touching it.
ONLY THEN, take the RAM out of the antistatic bag (by the edges only).