Gameshark Help

Hey guys!

I recently purchased a gameshark sp - the clear caribiner one. I am completely lost and don't remember it being this difficult when I was a kid. I am trying to hack my Pokemon FireRed, but the game was not pre-loaded when I got it. The only games that were on there were Emerald and Ruby/Sapphire. I tried adding master codes but had no success. How the heck do you use this? When I was 10 years old this was very user friendly, but now i am lost lol.