First and most important thing to do is deactivate or turn off the switch on the back of your unit.(tower or
computer). Secondly, make sure that you unplug the power cord that goes into your computer,which will have a female end with usually 3 slots.
Make sure that you will not cause any type of static electricity when you take the case off!!! This is why the computer parts come shipped or packaged in anti-static wrap or pouch of somesort. You can achieve this by not standing on a carpet even with sneakers or footware that may cause static, as it may ruin your memory by magnetizing the memory sticks.
If you have a computer that requires RAM Parity, which means you have to install 2 sticks that are equivilent in MB or it will not function, you will have to find some, it is usually in older computers. If it takes normal pc100 or pc133 RAM all you have to do is insert it into the slot next to your existing RAM and next time you start it, the computer should pick it up with plug and play, you have to do nothing, it will do it itself.
Make sure your RAM is not mixed with 1 of say, SD RAM and you want DDR Ram, you cannot mix the 2 they have to be either one type or another but not mixed in most cases. The motherboard should have the type of RAM it has marked next to the memory stick slots,if not remove the existing RAM and determine what type it is.
When you restart it again, go into your BIOS, by pushing delete when it boots up, then simply change the speed of the RAM . ex. 100/100, 100/133,etc.
You shouldn't have to do this last step. You will know when you try it out weather it is properly working or not on your last reboot. Good luck and don't get excited, it is nothing that anybody could charge you lots of money when you just need RAM installed if you encounter any diffecult situations. Have a Great Day, and Happy New Year !!!!