Before you record, you should check to make sure that the proper recording device is being used. To do so simply check the "Audio Setup" menu in Audacity.
The correct option should be the Shure MV7 microphone. Any anything else is selected, switch to the Shure MV7. To verify the microphone is working you can click the small microphone icon next to the "Share Audio" button. Then select "Start Monitoring". You will then see the levels of the microphone bounce around as you talk. It won't be recording at this point, but you can see that it is working.
Recording is very simple. Just hit the big red "Record" Button. A new audio track will be created and you will see the timeline move along as it starts to record the sound waves. When you have finished, simply press the "Stop" button and it will stop recording. You can preview your recording using the "Play" button. You can jump to a specific section by clicking on it.
To export your audio file go to File>Export> and select the file format you would like. MP3 and WAV would be the most common. MP3 will give a smaller file size and WAV will give a higher quality.