1. Get the power cable disconnected from your system. You can also remove the panel cables at the back so as to be able to lay down the system by its side.
2. In order for you to be able to gain access to the interior part of the system, you will have to get the side panel also disconnected, which is usually on the left side. The RAM slots are usually long and located around the right side of the processor. You can have about two to eight slots, where they have tabs or wings at the tip end. Press down the wing to remove the old RAM.
3. Check through the manual of your motherboard, and try to know where RAM would be, preferably located on the motherboard. Ensure you insert your RAM in the right way. Check the metal side of the chip and let the chip of the RAM be well intact with that of the motherboard.
4. When you are done with this, ensure that the wings are locked. Couple your system back, and boot it.