Right-click on Reason's rack window and select the ReDrum Drum Computer, NN-19 Digital Sampler or NN-XT Advanced Sampler from the "Create" menu. Every one of these machines will contain one or more small buttons with pictures of file folders on them. These are the buttons used for loading your samples.
Load your samples into the ReDrum Drum Computer if you would like to use them as part of a drum kit. This is also a good and fast idea if you have samples that require no modification or if you're just getting used to using Reason. Each drum or sample you use is assigned to some basic volume, pan and pitch knobs that can change where, when and how quickly it is triggered.
Import your audio clip into the NN-19 Digital Sampler to take it to the next level. The NN-19 is both a sampler and a synthesizer, permitting you to apply synthesizer effects to the sample. It contains knobs for altering the velocity and pitch of the sample, as well as a number of filter effects that may be applied at subtle or intense rates. The device is designed for loading many samples to work cohesively; however, its many functions, when applied, will globally affect every sample loaded into it.
Use the NN-XT Advanced Sampler for more complicated and detailed sampling projects. The NN-XT allows the user to load multiple samples at once and apply the device's modulation envelopes, pitch-shifting tools and spot-looping capabilities to them individually. The ability to apply different sounds with their own effects to each key on the device's virtual keyboard makes it possible to do anything from creating a sample library to writing an entire song within this single synthesizer.