The memory module slot in the Lenovo T400 laptop computer is located underneath the computer's palm rest. Because of this awkward location, some minor disassembly of the laptop is required to access the slot if you want to replace, upgrade or install new RAM. Some moderate computer expertise and a screwdriver are all that are required.
Turn off your laptop, close the screen, turn the computer over and remove both the battery and the power cable.
Use your screwdriver to remove the four screws on the computer labelled by a keyboard symbol.
Remove the palm rest by sliding it away from the keyboard and off of the computer, exposing the memory module slot beneath it.
Slide the currently installed memory module out of its slot and slide the new memory module into it.
Put the palm rest back onto your computer to cover and protect the RAM module.
Screw the four screws removed in Step 2 back into the computer, then replace the computer's battery.