1. In most laptops and possibly in the Dell M6400 laptop, memory / RAM can be found on the motherboard on two places. On the front and/or back of the motherboard. Depending on what side your memory is located (and possibly on both), you will either need to access the RAM memory by removing the front parts of the Dell M6400 laptop (Keyboard, Touchpad etc). The other place to find the RAM memory is on the back of the laptop. There is usually a RAM memory door to unscrew. Once its uncrewed, you can access the ram.
2. To replace or upgrade the RAM memory of your Dell M6400 laptop, hold both metal prongs to the side. The RAM memory card will release from the motherboard.
3. Gently hold the ram card on a 45 degree angle and remove the card.
4. Install your new replacement RAM memory on your Dell M6400 laptop.