Step 1: Click on the Microphone Icon on the Audacity Meter Toolbar to turn on monitoring. You should see a red level indicator moving slightly as it picks up room noise. Talk into the microphone and make adjustments to the volume until you get a level that bounces close to the top of the right edge without ever turning the far right solid red (which indicates you are clipping the audio). Once the level is adjusted, you're ready to record.
Step 2: Push the Record Button and start talking. When you finish recording press the stop button.
Step 3: Go to File > Save Project As to save your project. This will allow you to re-open your project later and edit.
Step 4: Go to File > Export Selection as MP3. Make sure you have the LAME MP3 Encoder installed before saving your file as MP3.