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Since you haven't told us what phone you have or what operating system your computer runs......


If on a Mac use redsn0w if you have an iphone 3gs or 4.

If on a Mac use absinthe if you have an iphone 4 s.
 
I'm gonna assume that you have an iPhone 4 w/ 5.0.1 based on your link; if so then:
You do not need to download the 5.0.1 firmware if you are already on iOS 5.0.1
You would skip step 2 of the tutorial; It says so right in the tutorial ;)
 
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