On the right lower side you can see the memory. The ASUS K50IJ has 2GB memory on board and usually comes with a 1GB memory stick (=3GB total RAM memory). The laptop can be upgraded to 4GB maximum, which means you can only use a 2GB stick (2GB PC2-6400 DDR2).

The memory stick is fixed with two holding clamps. Before you push these clamps aside, be sure that you are not electrostatic (go to the kitchen sink and touch the metal faucet to be discharged).

Now first push one holding clamp away from the memory stick. The stick will slightly pop up since it is under tension. Now push the other holding clamp, too.