I just want to see if I can do it / find it fun so I thought that turning my lamp on and off with my computer is a simple enough project can someone give me step by step instructions to do it or give me a link to some instructions thanks
Hi, start with the ArduinoInfo.Info WIKI.
In particular see the Power Control stuff here: http://arduino-info.wikispaces.com/ArduinoPower
The simple, low-cost solution is an optically-isolated relay board Like These
DISCLAIMER: Mentioned stuff from my own shop...
I would recommend you do not play with mains electricity for your first project try something with low voltages.
If you haven't been taught how to design electronic circuits dealing with mains voltages then I recommend that you use a commercial switch such as a powerswitch tail for that part. There are lots of ways that a DIY solution could put yourself or others at risk, and they aren't all obvious.