Follow these nn-xt-tagged tutorials to learn all about nn-xt with WonderHowTo's collection of free how-to videos and articles, like Add your own samples inside the NN-XT in Reason 3, Build samples with the NN-XT module in Reason, and Use Mod Envelope and LFO in the NN-XT of Reason 3.
You'll also find several great software tutorials in the Software category.