How to take long exposure shots on a NIKON D3100?

I want to take pictures with sparklers and write my name like this:

i'm really new to my nikon!

Put the selector on M (Manual). Press and HOLD DOWN the shutter release to take your picture, let go of the button when you are finished.

I think it's called "light grafitti". If you do a google search, it will explain how. (bulb mode, shutter release cable, tripod, etc.)