Launch Reason. When it loads, double-click the NN-XT graphic in the "Tool" window under "Instruments." Reason will instantiate the NN-XT sampler and display its interface.
Click the "Sample" button on the NN-XT interface. The "Sample" button is the button immediately to the left of the sample information screen, above and to the right of the "LFO 1 Rate" knob. It resembles a standard "Play" button.
Record your sample using the default audio input device. You can use your computer system's built-in microphone, if available, but you will achieve greater quality using an external microphone of some kind. A pop-up screen displaying the waveform of the sample in real time as it records will appear.
Click the "Stop Sampling" button in the pop-up window when you are finished recording your sample.
Click the "Edit" button in the pop-up window to call up the "Sample Editor" window. This window contains all of the standard editing tools found in most audio editing applications, such as "Crop," "Normalize" and "Reverse." Edit the sample to your liking and click "Save." The new sample will now be available for use in the "Unassigned Samples" window.