First, shut down the computer, turn off it's power switch and unplug the computer and connected
equipment from the wall. If you are not sure how to do this, take the system to a qualified computer technician. It's not worth risking your safety or accidentally destroying your expensive computer to save the expense of letting a professional do the job. Otherwise, proceed with the next steps.

Ideally, you should wear a grounded anti-static wrist strap when working on computer equipment, especially when handling memory and CPUs.  Also, the use of grounded anti-static mats on the floor and on the workbench is a good practice.  As a minimum, my advice is to make sure your body is touching the metal on the computer case when handling the CPU and the memory anytime between the time they are in their anti-static bag or container and installed on the motherboard and any time when directly touching them. Try to avoid touching drives, boards, memory, etc. with your clothes.  Clothing can quite often be charged with static electricity, especially during cold, dry Winter days. 

Many people don't realize that computer components can be damaged by static electricity and a problem won't appear until months later when a power surge, etc. completes the damage.  With the non-parity memory used in most recent computers, a damaged transistor in a memory chip can start corrupting files and you will not be alerted by an error message and not know about it until you see widespread results much later.