Well you can lay down your case first, on hardwood floor or a hardwood table. Touch the metal part of a case to discharge all static electricity, dont want to fry a componenet
If you are replacing the psu, take all the connections out. and Unscrew it from the outside of the case. Replace the new one in, and plug in all the necssary connections. If you are replacing the video card. locate the video card, and unscrew the screw that is holding it into the case, unplug the power cord if there is one. Push your new video card into the same slot, screw it down, and plug in the power connector.
Ram all you have to do is locate the ram slots. look into your mobo for dual channel ram to see what you have to put in which slots, usually its just slot 1 and slot 3. And look at the notch about 2/3 of the way from one end. THE RAM OHNYL GOES IN ONE WAY
. And line it up and push, make sure you push the clips on the side all the way in.
VV you can check my guide, link in my sig, to see some pictures