To help you through the basics of recording and editing audio in Audacity, the library has created a tutorial. Use the tutorial to help you walk through the step-by-step process.
We usually recommend recording audio through a microphone or separate recording device rather than recording through your computer microphone. This is because the computer microphone picks up sounds from your computer. However, the WASAPI Loopback feature can record the audio coming out of your computer and then remove it from the recording.
The envelope tool is used to shape the waveform of your audio track to increase or decrease the volume of the audio in specific sections
Create a control track (voice over) and then use the Auto Duck effect to automatically adjust the threshold level for background music.
Auto Duck analyzes the control track first of all, then applies the effect to the selected track(s). This second stage takes longer to complete than the first, so the estimated time remaining in the progress bar may be an underestimate until the later stages of processing.
More information can be found on the Audacity manual.
Metadata tags are stored with an audio file when you export the file and can be read by other programs such as iTunes. This includes information such as artist, album, track name, etc.